732 



S. W. WILLISTON 



arch, and is, hence, a true dorsal vertebra, leaving twenty as the 

 number of true cervicals, and three pectorals. The characteristic 

 structure of the cervical and dorsal vertebrae of Polycotylus latipinnis 

 is shown in fig. 13. 



Twenty-three presacral centra follow. They are all depressed 

 from pressure. The largest measures 42"^"^ in length and the series 

 1,300"^"^. The length of the neck is 700™™, that of the skull yoo™"', 

 giving a total length of the animal in life as about eleven feet, or 

 a little greater than that of the type specimen of T. Oshorni. 



Fig. 13. — Polycotylus latipinnis. a, twenty-sixth (last) cervical vertebra from the 

 side; b, the same vertebra, from in front; c, dorsal vertebra (forty -fourth of series) 

 from in front. All one-fourth natural size. 



Trinacromerum latimanus, n. sp. 

 Among the collections of the University of Chicago from the 

 Hailey Shales of the Upper Benton of Wyoming, are parts of two 

 individuals which I refer to an undescribed species of Trinacromerum 

 chiefly because of the absence of the second supernumerary epipodial 

 in the limbs and the character of the vertebrae. One of these speci- 

 mens has the posterior part of the skull, a number of vertebrae and 

 portions of the hmbs; the other, which may be taken as the type, is an 

 isolated humerus in perfect condition, collected by Mr. Roy Moodie 

 (fig. 15). From the humeri of T. hentonianum and T. anonymum it 

 differs conspicuously in its greater expansion distally. From the 

 humerus of Polycotylus latipinnis, which I here figure for the first 



