Sept. 25, 1884] 



NA TURE 



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for a very sensible progress in the evolution of organic forms. 

 The deposition of the Chalk commenced in the English area at 

 a period when the land floras were still of Jurassic character. 

 By the time it had reached Limburg, Saxony, and Bohemia, 

 Dicotyledons had become developed. The period required for 

 the chalk ocean to encroach but 300 to 400 miles mast thus have 

 been very vast. The question may, however, arise whether 

 plant development at this stage followed the otherwise universal 

 law of evolution, or was exceptionally rapid. The fauna has to 



• be examined to see whether it discloses an equally appreciable 

 progress. The conclusion arrived at is that while the groups 

 with which the author is less acquainted apparently do so, the 

 progress in the Mollusca" is unmistakable. The helicoid, tur- 

 binate, and patelloid groups are archaic and stationary, but the 

 fusiform shells betray a tendency to elongate their canals, and 

 the relative abundance of such, and gradual dropping out of 

 now extinct genera, furnish an unmistakable index of the relative 

 ages of the more littoral deposits. From this point of .view we 

 are able to demonstrate that the Greensands of Aix-la-Chapelle 

 are far younger than their lithological structure and sequence 

 would indicate, while the appearance ^of such distinctly new 

 developments as cone and cowry shells further support the 

 views of the relatively almost Tertiary, or, at least, transition, 



. age of the Cretaceous series in Denmark. While, therefore, 

 denudation on a truly colossal scale has produced one of the 

 most considerable gaps in the whole geological record between 

 Cretaceous and Tertiary over the British area, beds of inter- 

 mediate age may successfully be sought for at a distance from 

 this centre. The erroneous correlation of these, bed by bed 

 almost, with the typical Cretaceous series, as developed in 

 England, has led to a still more untrustworthy correlation of the 

 American series with ours. The Cretaceous series of America 

 contains at its very base a flora composed of angiosperms so 

 perfectly differentiated that they are apparently referable to 

 existing genera. One of the oldest floras in Europe containing 

 angiosperms is that of Aix-la-Chapelle, and even this we have 

 seen is relatively modern ; but these are not referable in at all 

 an equal degree to existing genera, and even the Conifene are 

 embarrassing on account of their highly transitional characters. 

 The oldest Cretaceous flora of America, so far from possessing 

 an)' Cretaceous characters, agrees in a remarkable manner with 

 that of the English Lower Eocene, while the Laramie, or sup- 

 posed Cretaceo-Eocene, flora has very much in common with 

 that of our Middle Eocene, and marks a similarly sudden rise in 

 temperature. The question is whether the evidence of the 

 fauna in favour 'of the Cretaceous age of the series is so con- 

 clusive that the floral evidence must be set aside. Taking the 

 Cretaceous series as represented in California, the older stages 

 possess Mollusca of definitely Cretaceous aspect, but those of 

 the newest have a decidedly Eocene facies. To be Cretaceous 

 a fauna must have some elements which did not survive to a 

 later period ; but are we in a position to state that the Am- 

 monitidse, the Belemnites, and Inocerami did not do so ? Even 

 our present limited knowledge is entirely opposed to such a 

 view. It must be remembered that the Eocenes in their typical 

 area, England and France, were deposited under peculiar local 

 conditions, and it would be as logical to infer from the absence 

 in them of Cretaceous types that these existed nowhere else as 

 it would be were the bed of the English Channel now upheaved 

 to class as extinct all forms of life not met with in its sands and 

 muds. If, as there is evidence to show, America was isolated 

 at the time, the survival there of forms of Reptilia elsewhere 

 extinct would be in accordance with ordinary observation at 

 the present day. The flora of the American series is Eocene ; 

 the fauna of its earlier stages is Cretaceous. We are compelled 

 therefore to choose whether we will believe that a large Eocene 

 flora was developed there during the Cretaceous, or that some 

 members of a Cretaceous fauna lived on to an Eocene date. 

 The former supposition demands greater rapidity of evolution 

 than we are accustomed to admit, and no external evidence is 

 advanced to support it. The latter is more conceivable from 

 the standpoint of evolution, and is not contradicted by any 

 evidence that has yet come under the author's observation. 



On\ Some Remains of Fish from the Upper Silurian Rocks of 

 Pennsylvania, by Prof. E. W. Claypole, B.A., B.Sc. (London), 

 F.G.S., of the Second Geological Survey of Pennsylvania. — The 

 earliest vertebrate animals yet known from any part of the world 

 are some remains of fish in the Upper Silurian rocks of England. 

 They are for the most part of three types. First, short fin- 

 spines, named by Agassiz Onchus tenitistriatus ; second, frag- 



ments of shagreen, or the skin of a placoid fish ( Thelidus and 

 Sphagodus), belonging probably to the same that carried the 

 spine; and third, ovate, finely striated plates or shields, sup- 

 posed to be the defensive armour of some fish, unlike any now 

 living. No one has doubted the ichthyic nature of the first and 

 second of these three forms. But as regards the third there has 

 been much controversy. Evidently allied to Ccphalaspis, its 

 right to the name of fish has been called in question, and suspi- 

 cion has been raised in regard to the whole family of the Cepha- 

 laspids. On the whole, however, it seems best to retain them in 

 the class of fishes, and to this conclusion Prof. Huxley evidently 

 inclines in the conclusion of his "Essay on the Classification of 

 the Devonian Fish." One may expect some, or even consider- 

 able, divergence of structure from the usual ichthyic types in 

 such early forms. These English fossils occur in the lowest beds 

 of the Devonian (Cornwall), and in the highest beds of the 

 Silurian (Shropshire and Hereford). The well-known Upper 

 Ludlow "bone bed" has yielded them in considerable quantity, 

 and one specimen is reported by Sir C. Lyell in his " Elements 

 of Geology" (1865) as discovered from the Lower Ludlow, 

 beneath the Aymestry limestone. Below this horizon I have 

 never heard of their occurrence. The English Ludlow, taken as 

 a whole, has been usually correlated with the Lower Helderberg 

 of North America, and on good grounds, both containing 

 Eurypterus and Pteiygotus. The English Lower Ludlow and the 

 Water-Lime or basal beds of the North-American Lower Helder- 

 berg are the lowest strata containing these fossils. On both sides of 

 the Atlantic they range from this level upwards into the Devonian. 

 The oldest vertebrate fossils yet announced from America are 

 those found in the Corniferous limestone or Lowest Devonian of 

 Ohio. Possibly the beds at Gaspe, on the Gulf of St. Lawrence, 

 are somewhat lower, as they have yielded Cefhalaspis, which is 

 not yet known from Ohio, and Coccostius, of which Ohio has 

 yielded only a single specimen. No authenticated fish-fossil has 

 yet been announced from the Upper Silurian rocks of America. 

 It is true that reports of the -discovery of such remains have 

 been published at various times, but investigation has proved 

 them all erroneous. (See " Palaeontology of New York," vol. ii. 

 pp. 319, 320, pi. lxxi. ; American Journal of Science, second 

 series, vol. i. p. 62; "Palaeontology of Ohio," vol. ii. p. 262.) 

 During my recent work on the palaeontology of Perry County, 

 Pennsylvania, I came upon some fossils which at once suggested 

 relationship to the Ludlow group above described. Among 

 them were a few spines recalling Onchus ttnuistriatus, but with 

 some differences. I have named them Onchus penny slvaniacs. 

 With them I discovered abundance of specimens bearing a strong 

 resemblance to Pteraspis, but larger, and differing in some other 

 respects. These I name Glyptaspis {G. clliptica and G. bitrun- 

 cata). Comparing these with Pteraspis we find them much 

 thinner, not exceeding one-tenth of an inch in thickness ; whereas 

 specimens of Pteraspis in my possession from Cornwall are 

 nearly one-fourth of an inch thick. The striation on both is 

 equally fine, but is rather less regular on the American speci- 

 mens. These also show no trace of the spine in which the shield 

 of Pteraspis terminates, as shown by Murchison in " Siluria." 

 No traces of the English fossil shagreen — TheloJus and Sfha- 

 godus — have been found in the Pennsylvanian beds, though it 

 abounds in the Ludlow rocks. The fossils were found in a bed 

 of sandstone about 200 feet below the base of the water-lime in 

 Perry County, Pennsylvania, near the top of the great mass of 

 variegated shale composing the Fifth Group of Rogers in the 

 First Survey of Pennsylvania. This shale in New York imme- 

 diately overlies the Niagara limestone, which is correlated on 

 satisfactory evidence with the Wenlock limestone of England. 

 Ten or twelve species are common to the two beds. It seems, 

 therefore, that the great mass of coloured shale, near the top of 

 which these fossils were found, and which is a continuation of 

 the Onondaga group of New York, has no representative in the 

 British series, but corresponds to an interval between the Upper 

 Wenlock and the Lower Ludlow. (For details regarding the 

 correlation of these beds in Pennsylvania with those in New 

 York, see a paper by the author in Proc. Amcr. Phil. Soc. for 

 1884.) It is consequently a necessary inference that the beds 

 yielding Glyptaspis and Onchus in Pennsylvania are somewhat 

 older than those containing Pteraspis and Onchus in England. 

 Microscopic examination of the specimens, and a comparison of 

 their structure with that of Pteraspis and Cephalaspis are in 

 progress, and the details will be given in the paper. Other 

 fossils in the author's possession indicate the possible existence of 

 fish at a still earlier date, but the material is not yet worked out. 



