June 18, 1869.] •*- ^ ^ [Cope. 



The fossil which Prof. Cope exhibited was the almost perfect cranium 

 of a Mosasauroid reptile, the Clidastes propython. He explained various 

 peculiarities of its structure, as the inoveable articulation of certain of the 

 mandibular pieces on each other, the suspension of the os-quadratum at 

 the extremity of a cylinder composed of the opisthotic, &c., and other 

 peculiarities. He also explained, from specimens, the characters of a 

 large new Plesiosauroid from Kansas, discovered by Wm. E. Webb, of 

 Topeka, which possessed deeply biconcave vertebrae, and anchylosed 

 veural arches, with the zygapophyses directed after the manner usual 

 among vertebrates. The former was thus shown to belong to the true 

 Sauropterygia, and not to the Streptosauria, of which Elasmosarus was 

 type. Several distal caudals were anchylosed, without chevron bones, 

 and of depressed form, while proximal caudals had anchylosed diapophy- 

 ses and distinct chevron bones. The form was regarded as new, and 

 called Polycotylus latipinnis, from the great relative stoutness of the 

 paddle. 



He also gave an account of the discovery, by Dr. Samuel Lockwood, of 

 Keyport, of a fragment of a large Dinasaur, in the clay which underlies 

 immediately the clay marls below the lower green sand bed in Monmouth 

 County, K- J. The piece was the extremities of the tibia and fibula, 

 with astragal o-calcaneum anchylosed to the former, in length about 

 sixteen inches ; distal width fourteen. The confluence of the first series 

 of tarsal bones with each other, and with the tibia, he regarded as a most 

 interesting peculiarity, and one only met with elsewhere in the reptile 

 Compsognathus and in birds . He therefore referred the animal to the 

 order Symphypoda, near to Compsognathus Wagn. The extremity of 

 the fibula was free from, and received into a cavity of the astragalo-cal- 

 caneum, and demonstrated what the speaker had already asserted, that 

 the fibula of Ignanodon and Hadrosaurus had been inverted by their 

 describers. The medullary cavity was filled with open cancellous tissue . 

 The species, which was one half larger than the type specimen of Hadro- 

 saurus foulkii, he named Ornithotarsus immanis. 



Dr. H. C. Wood spoke of his investigations witli regard to 

 tTie Fresh Water Alg93 of Eastern North America. 



Pending nominations, Nos. 628 to 638, new nominations, 

 Nos. 638 to 6iO, were read. 



Dr. H. Allen offered and read a paper " On Human Oste- 

 ology, containing the heads of divisions of a more extended 

 commnnicatioii, which he proposes to present at a future 

 time. 



