18 



PROCEEDINGS OF THE ACADEMY OF 



It is worthy of uote in this connection, that there are various other fossils 

 in the upper members of our lower Carboniferous series that might with quite 

 as much propriety be referred to European Permian species as many of the 

 Western Coal-measure types that have been so referred. For instance, Dr. 

 Prout long since (Trans. St. Louis Acad. Sciences, vol. I. p. 450) identified a 

 Polypora, from the Chester beds, with the Russian Permian P. biarmica ; while 

 several other species of Polyzoa found in the Chester group are scarcely dis- 

 tinguishable from forms found in western beds that have been by some in- 

 cluded in the Permian. We also now know that there are species of Schizodus, 

 Pleurophorus, etc., in the Chester beds very like Permian forms ; while a Cri- 

 noid, found by Prof. Marcou in beds in Nebraska (referred by him to the Per- 

 mian), and thought by him to be " extremely near Encrinus moniliformis, Miller, 

 of the Muschelkalk of Europe,'' is now known to range through the whole of 

 the Western Coal-measures, and to be represented in the Chester limestone 

 beneath the Millstone-grit by closely allied species. Indeed, a number of 

 Crinoids that have been recently discovered in the Chester beds and the Coal- 

 measures of Illinois are remarkably similar representative forms. Even the 

 curious Zeacrinus mucrospinus of McChesney, from the Upper Coal-measures of 

 Illinois, has its nearly allied representative in the Chester limestone below 

 the Millstone-grit. 



Numerous facts like the foregoing (such, for instance, as the occurrence of 

 Tertiary types of plants in the Nebraska Cretaceous), might be cited to show 

 that in many instances particular forms of life, both animal and vegetable, 

 appeared here at earlier periods than in the old world. Hence, great caution, 

 and some general knowledge of the entire fauna and flora of our rocks, are 

 often required in order to arrive at sound conclusion with regard to their re- 

 lations to particular horizons of the series, as made out in Europe. 



April 5th. 

 Dr. Carson, Vice-President, in the Chair. 

 Twenty-three members present. 



Professor Leidy made the following remarks on Discosacrcs and its Al- 

 lies. 



The body of the last vertebra in the series of caudals belonging to the Kan- 

 sas saurian, described by Prof. Cope under the name of Elasmosaurus, has the 

 length less than the depth or breadth, which latter is the greatest diameter. 

 It is moderately contracted towards the middle, the sides below the neural 

 arch and the surface below the costal articulations being fore and aft concave, 

 and bounded in front and behind by an acute margin from the articular ends. 

 A ridge extends fore and aft between the chevron articulations and the in- 

 cluded surface is concave, and exhibits a single lateral venous foramen. The 

 costal articular processes project from the middle of the side of the body, 

 reaching nearer the fore than the back end of the latter. They are transversely 

 oval, about three-fourths the length of the body, and the height about half. 

 They form a deep concavity, with acute margins expanding peripherally. 

 The articular ends of the body are transversely oval and defined from the 

 intermediate portion of the latter by an acute everted margin. A short dis- 

 tance within the position of the latter the surface is marked by a narrow 

 groove, and within the circle of this groove the surface projects in such a manner 

 as to appear like a distinct disk or epiphysial plate applied to and eoossified 

 with the body. The surface of the disk is convex at the periphery and 

 moderately concave towards the centre. The articular surface beyond the 

 groove denning the disk appears as an everted ledge, and the triangular articu- 

 lar facets for the chevrons appear as deflections of the ledge. The extension 

 of the latter inferiorly is greater at the posterior extremity of the body than 



[April, 



