NATURAL SCIENCES OF PHILADELPHIA. It 



If the hollow interior be the natural condition of the Mylodon-YOka humerus 

 under inspection, it would not belong to Mylodon robwtue. Independently of 

 the cavity indicated, the bone is sufficiently different in size and form to indi- 

 cate a different species from the Mylodon Harlan, of North America. The hu- 

 merus from Oregon, described by Perkins (Am. Jour. Sci. 1841, xlii, 136), and 

 referred to the latter by Prof. Owen, is not only much larger, but it is of 

 greater breadth in relation with its antero-posterior diameter. The fragment 

 of a humerus from Big-Bone-Lick, Ky., represented in fig. 3, plate xiv of my 

 "Memoir on the Extinct Sloth Tribe," is somewhat smaller than the corres- 

 ponding part of the Oregon specimen, and is more compressed or wider in 

 comparison with the antero-posterior diameter. 



Prof. Leidy further observed that there appeared to be a point of some sig- 

 nificance in the anatomy of the mandible of Dromalherium silvestre worthy of 

 attention, though the appearance may turn out to be a deceptive one. Prof. 

 Emmons had discovered three isolated rami of mandibles of this most ancient 

 of American mammals in the triassic coal of North Carolina. Of the speci- 

 mens, one is represented in fig. 66 of Emmons' American Geology, repeated in 

 outline in fig. 650 of Dana's Geology. Another specimen Prof. Emmons pre- 

 sented to the Academy, and is contained in our museum. The point of inter- 

 est to which reference is made is the apparent absence of a condyle. This 

 process may have been lost, but in the two specimens seen by Prof. L. that 

 figured by Prof. Emmons, and that preserved in our museum a separation of 

 the process is not obvious. 



March 8th. 

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

 Twenty-five members present. 



Prof. Leidy made the following remarks : The reptilian remains from the 

 cretaceous formation near Fort Wallace, Kansas, presented to the Academy by 

 Dr. T. H. Turner, and described by Prof. Cope under the name of Elasmosaurus 

 platyurus, belong to an Enaliosaurian, as originally suggested by Prof. Cope. 

 The anatomical characters of the different regions of the vertebral column, 

 those of the shoulder and pelvic girdles, and of the preserved portions of the 

 skull and teeth, are decidedly Plesiosaurian. 



Prof. Cope has described the skeleton in a reversed position to the true one, 

 and in that view has represented it iu a restored condition in fig. 1, pi. ii. of 

 his "Synopsis of the Extinct Batrachia and Reptilia," Pt. I, August, 1869, 

 published in advance for the fourteenth volume of the Transactions of the 

 American Philosophical Society. To explain the apparently anomalous and 

 reversed arrangement of the articular processes (zygapophyses) of the verte- 

 bra?, he has supposed that those as ordinarily existing are substituted by the 

 second set of articular processes (zygophene and zygantrum), as found in 

 serpents and iguanians (Proc. Bost Nat. Hist. Soc. xii, 265 ; Syn. Ext. Bat. 

 and' Rept. 42). 



The finding of a portion of the jaws, as reported by Dr. Turner, in the vi- 

 cinity of what Prof.Cope has supposed to be the cervical portion of the 

 skeleton, and which he considers as confirmatory of the view he has taken 

 of its position, without further consideration, is more than compensated in the 

 opposite end of the column terminating in a coossified axis and atlas, as is the 

 case also in the mature Plesiosaurus. The cup of the atlas still retains the 

 hemispherical occipital condyle. 



The Kansas saurian was wonderful for the length of its neck, far exceeding 

 in this respect the Plesiosaurus. The vertebrae in the specimen form a nearly 

 unbroken series to the seventy sixth inclusive. If we regard all as cervical 

 until the transverse processes begin to spring in part from the spinal arch, it 



1870.] 



