10 PROCEEDINGS OF THE ACADEMY OF 



will comprise the extraordinary number of seventy-two. In the different spe- 

 cies of Plesiosaurus, so far as known, the number ranges from twenty-four to 

 forty-one. The length of the neck, independent of the head, was about twenty- 

 two feet. 



The cervical vertebrae successively increase in length to about the forty- 

 fourth, then remain nearly the same to the sixtieth, and afterwards gradually 

 decrease. The atlo-axis is about 2} inches long; the third cervical is 1 

 inches ; the tenth nearly 2 inches ; the twentieth 2J inches ; the thirtieth 3J 

 inches; the fortieth 4 inches ; the forty-fourth 4} inches, and so to the six- 

 tieth ; and the sixty-eighth to the last one about 3| inches, which is also about 

 the length of the succeeding four dorsals. 



The imperfections in the remainder of the vertebral column of the Kansas 

 saurian do not permit a positive estimate to be made of the comparative ex- 

 tent of the trunk and tail. 



A comparison cf the caudal vertebra; with isolated specimens from the cre- 

 taceous formations of Alabama, Mississippi and New Jersey, leaves but little 

 doubt that Elasmosaurus is identical with Disco sour us. Such also appears 

 originally to have been the opinion held by Prof. Cope in regard to a portion 

 of the same skeleton, which he referred to a species with the name of Disco- 

 saurvs carinatus (LeConte's Notes on the Geology of the Survey of the Union 

 Pacific Railroad, 1868, p. 68). 



Specimens of vertebral bodies from the New Jersey green sand, referred to 

 Cimoliasaurus (Cret. Rept. of the United States, pis. v, vi), and supposed by 

 me to belong to the posterior part of the column, are seen by comparison with 

 the Kansas skeleton to be cervical and perhaps anterior dorsals. The differ- 

 ence in the proportions of the corresponding vertebrae appear to indicate the 

 genus to be distinct from Discosaurus. 



The imperfect vertebral specimens from Arkansas, originally referred to 

 Brimosaurus (Pr. Acad. Nat. Sci. 1854, 72, pi. ii, figs. 1 3), are probably pos- 

 terior cervicals of Discosaurus. 



In the true view of Discosaurus and its allies, the so-called order of Strepto- 

 sauria (Proc. Bost. Nat. Hist. Soc. 18G9, 265 ; Synopsis Ext. Batr. and Rept., 

 40) fails to maintain its position. 



The extensive shoulder and pelvic girdles of the Kansas saurian, so much 

 like those of Plesiosaurus, were most probably provided with limbs constructed 

 like those of the latter animal. 



In its restored condition Discosaurus would appear to have resembled Plesio- 

 saurus in its form as ordinarily represented, excepting that it possessed a much 

 longer neck, one indeed that exceeded that of all known animals. We may 

 imagine this extraordinary creature, wilh its turtle-like body, paddling about, 

 at one moment darting its head a distanee of upwards of twenty feet into the 

 depths of the sea after its fish piey, at another into the air after some feathered 

 or other winged reptile, or perhaps, when near shore, even reaching so far as 

 to seize by the throat some biped dinosaur. 



Prof. Leidy subsequently exhibited fragments of a fossil mandible, upon 

 which he made the following remarks : The specimens were obtained by Prof. 

 F. V. Hayden from the tertiary rocks of the Bridger Group, near Fort Bridger, 

 Wyoming. They indicate a carnivorous animal, apparently of an extinct and 

 heretofore unknown genus. Unfortunately the teeth are lost, except portions 

 of some of the molars. The animal was larger than our Panther, and proba- 

 bly was a member of the same family, but with a relationship to the Ilyamas. 

 The portion of the jaw preserved nearly agrees in form with the corresponding 

 portion in the Cats, but its depth below the position of the teeth is propor- 

 tionately greater, resembling in this respect more the condition in the Striped 

 Hyajna. 



Remains of the canine alveolus indicate a tooth of more robust proportions 

 than in the latter animal. The symphysis pursues the course of the alveolus. 



[March, 



