Abstract
LONDON
Geological Society, January 24. Mr. Joseph Prestwich, F.R.S., president, in the chair.-The following communications were read:-(i) "On the Foraminifera of the Family RotalinEe (Carpenter) found in the Cretaceous Formations, with Notes on their Tertiary and Recent Representatives,“by Prof. T. Rupert Jones, and Mr. W. K. Parker, F.R.. S. The authors enumerated the RotalinEe which hive been found in the Cretaceous rocks of Europe, and showed by tabular synopses the range of the species and notable varieties in the different formations of the Cretaceous system. For the comparison of the Tertiary RotalinEe with those of the Cretaceous period the following Tertiary formations were selected:- the Kessenberg beds in the Northern Alps, the Paris Tertiaries, the London Clay, the Tertiary beds of the Vienna Basin, and the English and Antwerp Crags. The authors also enumerated the recent Foraminifera of the Atlant-c Ocean. The authors stated that of Planorbulina several species and important varieties of the; compact, conicil form occur throughout the Cretaceous series, and that those of the Nau iloid group are still more abundant. The plano-convex forms are represented throughout the series by P. (Jruncafulina) lohatula; but the flit concentric growths had not yet come in. Planorbulina extends down to the Lias and Trias. Pulvinulina npanda is f-ebly represented in the uppermost Chalk, but forms of tha "Menardii“group abound throughout the series. Species of the "elegans“group are peculiarly characteristic of the Gault, and some of the “Schreibersii“group are scattered throughout. These two grotxps extend fir back in the Secondary psriod. The typical Rotali-i Bi-ccarii is not a Cretaceous form, hut the nearly allied R. itnMlicata is common. Tinoporus and Patdlina occur at several stages; Calcarina only in the Upper Giaik. The above-mentioned types are for the most put still Jiving, but the “auricula “group of Puhinulina is wanting in the Cretaceous series, as also are Spirtllina and Cymbalnpom, except that the latter occurs in the Maestricht C.ialk, Discorbina and Calcarina make their first appearance in the uppermost Chalk. Tne chief distinction between the Cretaceous and the existing RotalinEe as said to consist in ths progressively increasing number of modifications. The authors concluded by disputing the propriety of regarding the Atlantic ooze as homologous with the Chalk. The president suggested the possibility of some of the minute Foraminifera being transported fossils derived from earlier beds than those in which they are now found. Dr. Carpenter observed that the mode of examination to be adopted with Foraminifera was different in character from that which was applicable to higher organisms. The range in variation was so great that an imperfect examination of Nummulites had sufficed to make M. d'Archiac reduce the number of species by one half; and all the speaker's subsequent studies had impressed upon him the variety in form and iri sculpturing of surface on individuals of the same species. When out of some thousands of specimens of OpercuUim, say, a dozen pronounced forms had been selected, such as by themselves seemed well marked and distinct, it might turn out that after all there was but one species present with intermediate varieties connecting all these different forms. He thought the same held good with RotalinEe, and that there were osculant forms which might connect, not only the species, but even the genera into which they had been subdivided. This "fact had an important bearing on their genetic succession, especially as it appeared that some of the best-marked types were due to the conditions under which they lived. The temperature in tropical seas differed in accordance with the depth so much, that when 2,000 fathoms were reached a degree of cold was attained such as was to be found in high latitudes; and in consequence the deep-sea forms in tropical latitudes assumed the dwarfed character of those in shallower seas and nearer the pole. He suggested caution in drawing inferences from forms so subject to modification, bolh spoiltaneous and due to the depth of the sea, especially as connected with abundance of food. Prof. Ramsay remarked that geologists would be pleased to find Foraminifera exhibiting, like other organisms, changes in some degree connected with the lapse of time. Tttese low forms, however, could hardly afford criteria for judging of the age of geological formations, while at the same time such ample means were afforded by the higher organisms for coming to a conclusion. He cited, for instance, the Cephalopoda, as proving how different were the more important forms of marine life in Cretaceous times from those of the present day. He thought that no one who had thoroughly stud ed the forms of ancient life would be led to ignore the differences they presented, as a whole, from those now existing. Prof. Jones, in reoly, observed that the question of whether the Foraminifera in a given bed were derived or not was to be solved partly by their condition and partly by their relative proportions, but that in most cases sufficient data existed on which to found a judgment. He'agreed wish Dr. Carpenter as to the existenc. of extreme modifications, and it had been his object to ignore such as seem due to ordinary and local causes, and to group the forms in accordance with certain characteristics. Whether the classification was right or wrong, it was necessary, for the sake of increasing knowledge, that fossils of this kind should be arranged in groups; and whether these were to be regarded as truly generic was a minor consideration. In forming their types and subtypes the authors had carefully avoided minor differences; but they still thought that the modifications which were capable of being substantiated were significant of a great lapse of time. A variation once established never returned completely to the original type. In Globigerina. he stated that there were in Cretaceous times 8 forms, in Tertiiry 12, at the present time 14; and these modifications he regarded as equivalent to the specific changes in higher animah.(2.) "On the Infralias in Yorkshire,“by the Rev. J. F. Blake. The Infralias, i.e., the zones of Ammonites planorbis and Am. angulatus, have been recorded hitherto only from Redcar, to the beds at which place the author referred; but the chief object of the paper was to describe some ssciions at Cliff, near Market Weighton, where these and lower beds are well exposed, and have yielded a numerous suite of fossils. He considered, however, that these beds did not belong to the typical Yorkshire area, but were the, thin end of the series wh ch stretches across England. He supposed there had been a barrier ia Carbomferous times, which had separated the coal-fields of Yorkshire and Durham, prevented the continuity of the Permian beds, and curved round the secondary rocks to the north of it, to form the real Yorkshire basin, while these beds at Cliff were immediately to the south of it. The sections described were six in number, the first pit yielding the great majority of the fossils, and the third showing best the succession of the beds. The fossils could be mostly identified with known forms, and showed a striking similarity to the Het-tangian fauna. In all the clavs of the Infralias Foraminifera were numerous and varied. The section in pit No. 3 showed, commencing at the top:-1. Stone bed with Am. angulatm (the fossiliferous bed of pit No. l). 2. Thick clays, with bands of stone characterised by Am. Johnstoni. 3. One band of clay with Am. planorbis. 4. Thin-bedded stones and clays, some of them oyster-bands. 5. Clays without Foraminifera, and with impressions of Anatina (White Lias). The Avicala, contorta series is not reached, nor are there any signs of the bone-bed, as the junction with the Keuper marls, which are found three miles off, is not seen. The paper was followed by references to the fossils mentioned, including the description of those that are considered new. Prof. Duncan remarked that English geologists had been backward in receiving the term Infralias, which he had suggested with respect to the Sutton Down beds some years ago, and the propriety of which was shown by the term having been applied to the same beds by French geologists at a still earlier period. As to the White Lias, he regarded it as a mere local deposit, not to be found out of England. He traced the existence of the Infralias from Luxembourg through France into South Wales, where corals were abundant. In Yorkshire, though one fine coral had been found, the Ammonites seemed to point to a difference in condition. Mr. Hughes remarked that the lithological character of the beds, as described by the author, did not agree with that of the Infralias in the S. W. of England or the N of Italy, and that the palaeontological evidence which had been laid before the Society did not confirm the view that they were Infralias, the author having especially noticed the absence of Avicula. contorts where he expected that it should occur. Also, by reference to the author's section, Mr. Hughes pointed out tint below what he described as Intralias he drew other beds which were not Trias, the author having explained that some beds which had been called Trias were only stained beds of Liassic age. The Rev. J. F. Blake, in reply, acknowledged the difference between the Yorkshire section and those of the neighbourhood of Bath, but insisted on the similarity of the fossils.
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Societies and Academies . Nature 5, 294–296 (1872). https://doi.org/10.1038/005294a0
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DOI: https://doi.org/10.1038/005294a0