Bulletin of Museum of Comparative Zoology 28

BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY HARVARD COLLEGE, IN CAMBRIDGE VOL XXVIII (Geological Series, III.) CAMBRIDGE, MASS., 1895-1898 U S A \ University Press: John Wilson and Son, Cambridge, U.S.A 61333g + s-S" CONTENTS No - of No — Fossil Sponges of the Flint Nodules Texas — The on the By J A Merrill Elevated Reef Geology of Pagk in the Lower Cretaceous July, 1895 (1 Plate.) By of Florida Southern Florida By A Agassiz L S Griswold With Notes (26 Plates.) October, 1896 No — Notes 27 on an Artesian Well sunk at Key West, Based on a Collection made by A Agassiz By E O Florida, in 1895 Hoyey Decem- ber, 1896 No " 63 — A Visit to the Great Barrier Reef Croydon," during April and May, 1896 of By Australia in A Agassiz the Steamer (42 Plates.) April, 1898 No 5, — The tions of By 95 Geological History Costa Rica R T Hill of the Isthmus of Panama and por- Based upon a Reconnoissance made for A Agassiz (19 Plates.) June, 1898 149 No — By of Texas The Nodules in Fossil Sponges of the Flint Lower Cretaceous the A Merrill J following investigation was undertaken as thesis work in the course in Palaeontology in Harvard University, at the suggestion of the instructor, Dr li somewhat and publish N As the study proceeded, T Jackson became more apparent and it it was thought advisable With the advice and assistance of Professor S Shaler, therefore, careful revision So here presented far as I importance its to extend the work has been made and the results have been able to ascertain, the minute structure of the cretaceous Hints of America has never been studied except in a general way, and nothing whatever has been published on the a a fascinating one, as only as a beginning The inquiry of what in and this will prove hoped is which nodules from flint study were collected size field effort is therefore is intended a fruitful line of specimens were taken for a quarry near Austin, Texas, and brought to They vary Cambridge by Mr Edward E Cauthorne and The organisms composing them microscopic large as well greatly in shape and, owing, perhaps, to small areas of calcite scattered through ; the mass, they vary somewhat in greater than that of glass, and the shape they are spherical, cylindrical, or two inches to a foot or more flat diameter iu The hardness hardness flint will ; and The in silica ; varying in size These spots replacements of organic remains, and, when such, examined, chalcedonic a dense black, is it, In they vary from size color with white or gray spots mixed irregularly through from microscopic to that of a pin-head often is generally scratch glass are generally are, in all cases that I the larger ones showing the concentric structure characteristic of chalcedony Some of them, however, have shapes so irregular and outlines so indefinite, that they cannot be referred to any particular organic form, although they are most replacements indefinite in the All spots of form and outline their behavior in polarized light calcite examined are small likely and They are called calcite because of The outside of the nodule is com- posed of a layer of chalk about one quarter to three quarters of an inch Contributions from the Geological Laboratory of the Zoology, in charge of N VOL XXVIII — NO S Shaler Museum of Comparative BULLETIN thickness, iii : MUSEUM OF COMPARATIVE ZOOLOGY cemented with ing with layers of solid, Generally, there infiltration of silica one layer of chalky substance, but one nodule in amorphous I found is but four, alternat- giving the whole the ringed silica appearance of a concretion of sand or clay Of the occurrence and appearance of these nodules in situ, I quote the following from the First Annual Report of the Geological Survey of Texas, by Professor Eobert T Hill (pp 124, 125) : " These fliut nodules are found and chalky limestone subdivision of the Comanche They are oval and kidney-shaped, Series of the Cretaceous of Texas ranging in size from that of a walnut to about two feet in diameter in the Caprina chalk Exteriorly they are chalky white, resembling in general character the flint nodules of the English chalk Interiorly they are of various cliffs shades of color from light opalescent to black, sometimes showing a banded structure so far, at least, as is The fact that these are the only flint horizons, known to the writer, in the whole of the immense cretaceous deposits of the United States, cially since is very interesting, and espe- they occur about the middle of the Lower Cretaceous Series, Upper Series as in England." The nodules of Comanche County, according to Professor instead of the top of the nucleus, Monopleura Texana, around which the flint Hill, contain a has formed, but in the nodules that I examined the silica was solid throughout and there The work herein described was confined were no nuclei of any kind largely to three nodules, which were prepared Thin sections were cut and mounted slides are made in the following way Cauada balsam, just in as rock These sections were made at for petrographical study the circumference and near to the centre, perpendicular to the surface and approximately parallel to were made at random in In addition to these, several slides it each nodule This precaution was observed in order that the difference in preservation of organic remains between the interior and surface might he detected, CHt at different angles to detect arrangement of organic remains if in even a short period of time present the nodule, result from the constant application of for if The sections were there be a tendency toward definite — a tendency which might any external force unchanging Caustic potash and acids were tried in identifying the mineral material of the replacement, but on account of the very hard nature of the mass of the nodule, it was found best to use the polarizer only, which produced more satisfactory results the progress of this work, I During have been the recipient of favors from Dr Robert T Jackson and the Boston Society of Natural History, both of winch it is my pleasure to acknowledge MERRILL A A : FOSSIL SPONGE SPICULES Statement of the Questions Involved detailed statement of the questions involved in this inquiry mind of service in directing the to the result may be from the beginning, thus placing before the reader the distinct line of thought to be followed The excellent work done on cherts and Hints by Carter, Sollas, and Hinde in England, and Zittel and others on the Continent, has conclusively shown that the source of these stones is organic silica, and that the principal source of this silica is the framework of siliceous sponges have therefore assumed this origin for the silica of the flint nodules under consideration This conclusion appears admissible from the great similarity of physical characteristics of nodules and surrounding materials in the Cretaceous of Europe and America, and also from the fact that the included fossils same are of the and genera families forms, and the comparison of The The identity of origin assumed, there us the profitable task of the identification of the organic left for is still them with the known forms of Europe following topics, therefore, will be discussed in the order given: The sented identification These fossils — of the fossils of the groups of animals repre- cover rather a wide range and are significant as well as interesting As attention fossils is and of sponge spicules are the principal organic remains, next drawn to a consideration of the condition of preserva- character of replacement of these spicules The forms of up and classified to the genus, where it is posby comparison with work done by others in this subject tion spicules are then taken sible, Since the microscopic structure of flint nodules has not been would seem that the question of condition and process of formation might receive some attention If we suppose that the nodules are segregations of materials from many sponges, collected around a nucleus which occupies a position near the centre, then all studied before, the spicules it from centre to circumference would show considerable mechanical wear as the result of concretionary formation hand, if we suppose the nodules cluster of to have growing sponges, which die then the spicules of sponges in situ, On the other been formed at the hnse of a in all stages of development, so far as they have escaped the process of solution, will be perfectly preserved ; while the spicules from the surrounding sponge areas washed in show more or In this case a foreign bodv as less mechanical wear by motion of the water, will BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY nucleus nodules may or may not be present It is evident also that different may have been formed in different ways, and hence we shall confine our conclusions to the limits of our observations In the summary we shall discuss the bearing of this study on the depth and condition of deposition of the chalk of the surroundiug formations Organisms found Slides taken from the in the Flint same nodule were found to present great simi- larity of kinds of organisms, but great difference in spicule, for instance, is often same in all stages A size species of of development nodules, however, show great variation Different slide found in the in the prevailing kinds of organisms and the condition of their preservation On the whole, however, the massive number of organic remains When greatly in excess silica is few, and the viewed with high power of microscope, this massive portion appears often to consist of aggregations of minute granules varying in color from Dr Hinde found the same true the granules as of spherical form." structure are brown in cherts of the to almost colorless Greensaud, and speaks having " circular outlines, though not strictly a Chalcedonic masses with their characteristic concentric common in some of the nodules and rare in others Many traces of organisms, the outlines of whiGh were but dimly shown, were not made out ; but those determined were of the groups given below Foraminifera These were found were quite numerous in in every slide examined, and one of the nodules The types found were principally of the family Globigerina, of which several different species Textularia were found in most of the slides, though not so were common common as Globigerina, and several other families were found occasion- These forms were generally replaced by amorphous silica, the substance which has the appearance of ally outlines remaining in a dark Globigerina were also found replaced organic residue silica, in chalcedonic but the outlines and structure of the chalcedonic mass almost obliterated the form of the fossil two of the nodules the spicules were of frequent but in one nodule of which I had occurrence, but not very abundant Sponges In ; two fragment of the spicule nute dermal spicules Part was found, except occasionally a small shown in Figure The mia Monactinellid of sections, not a distinct trace Sponge Remains II., 1885, p 127 of are, generally speaking, better preserved than the Lower ami Qppei Greensand, Phil Trans Royal Society, MERRILL : FOSSIL SPONGE SPICULES zone spicules, and are therefore present in greater numbers These will be discussed in detail later Mollusks Small fragments of what I thought nacreous and pris- matic tissue of shells of mollusks were found in two of the nodules The condition of their preservation was not sufficiently perfect, however, make their identification absolutely certain They are replaced by amorphous silica, which in taking their structure has been turned a to bright transparent yellow Fishes Several organisms having the general form of fish scales were found, but no attempt has been made to identify them with modern or fossil fishes They appearance of organic are of a bright transparent yellow, and have the silica Their surfaces are perfectly smooth, and the outline entire and complete different In the polarizer they show no effect from that produced by the amorphous silica surrounding them I concluded, therefore, that they are amorphous silica similar to the shell fragments previously described Condition of Preservation of the Sponge Spicules Spicules are found in these flints in all stages of preservation But few were found perfect except the globo-stellates and similar spicules of the dermal layer numerous they Occasionally, areas in the slide were found containing faint tracings of spicules cannot be separately traced which are so merged together that More often, however, they are Under the high power of the microscope, except in cases where the spicules seem to end indefinitely in the surrounding silica, the outline is perfect, but more or less ragged, owing to the irregularities of replacement The canal often shows a separate crystallization from the body of the spicule, and is generally smooth in outline The canal differs greatly in size in the different specimens, and in some occupies the entire body except a small ring of separately embedded in a crystalline silica on the mass of amorphous outside Apparently the replacement began along the axial canal at the same time as some cases, as in Figure 5, it silica it did on the surface, and in seems that most of the spicule has been replaced from the inner side In this spicule, and also in others, the canal seems to be replaced with a dark opalescent silica mixed with grains of siliceous sand Replace- ments with sandy material are common In other spicules the canal and in a is in the English flints perfectly transparent and hyaline in appearance, few cases the canal is not continuous (see Figure 1) In BULLETIN MUSEUM OF COMPARATIVE ZOOLOGY : those spicules that have canals the polarizer shows plainly two distinct areas of crystallization, the outer one being the more In those perfect spicules that have no separate replacement of the canal, the whole is replaced by amorphous The globo-stellates and other somewhat different appearance silica, spicule in many In cases these are Spicules the globule, the spine, and the minute barbs being entirely perfect, perfect generally of an opalescent hue spicules of the dermal layer present a The color of these spicules more or less transparent, In polarized light these have the same their microscopic details all brown varies from a light and some of them quite to a dark yellow, all so amorphous silica, with the exception of color and a One case was found where the globo-stellate higher single refraction had been replaced by crystalline chalcedonic silica, but it was imperfectly properties as the preserved, and the barbs on the spines were so short and poorly finished This fact clearly shows us that we it was not possible to figure it must suppose either that the spicules have been replaced by amorphous that silica, or that they are in the still hyaline or colloidal state as formed, and colored yellow by some organic agent perhaps While this latter supposition seems most reasonable from the fa«ts considered, yet if such be the case it would seem probable that some spicules would be found partly replaced with crystalline discovered necessary to limited, silica, However, before we admit remember that the and that such may field the spicules as colloidal original condition in for silica, recognizing the fact that it which phenomenon which was not doubt to value, its full of observation was exist in sufficient I shall designate this of replacement a this number to it is extremely show all Btagea transparent yellow condition of want of a better term, same time at the has changed considerably in color from the it was secreted by the animal While the preservation of many of the globo-stellates is perfect, even to the showing of the minute spines and barbs in the proper relation to the globate centre, yet some of them appear in a more or less fragmental Some show condition, which reveals an interesting fact in their history the spines and barbs bent slightly toward the central body, as in Figure lL'; in others the barbs are broken off or otherwise removed, and are missing entirely ; removed, as while in others the globate portion of it is due to mechanical at least part of is it in is Figure 13 force due it is How much is broken and part of this breakage and removal difficult to say, fur there is to solution dissolved more quickly and easily than the spines, hut the spines will yield first to evidence that It appears that the globulai centre any mechanical force it, is plain that Sollas found by ~ : fc: < o _l o > CO < o a Li O cc h < C o ... quarters of an inch Contributions from the Geological Laboratory of the Zoology, in charge of N VOL XXVIII — NO S Shaler Museum of Comparative BULLETIN thickness, iii : MUSEUM OF COMPARATIVE ZOOLOGY. .. 30 BULLETIN 16 MUSEUM OF COMPARATIVE ZOOLOGY : spines The slight curve of the spines cesses Size : name Geodiaf smooth between the from of Body propose the Geodia? Figure 14 ular ; Size of bifurcation... BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY 12 Annals and Magazine of Natural History References to other works are cited at the places where quotations occur, in order that investiga- may tion of