155 



A series of' twenty-nine caudal vertebrae, with and without diapophyses, 



from a bluff' on Butte Creek, belongs perhaps to this species. The proximal 



specimens, at least, cannot be distinguished from those of Professor Muclge's 



collection. The distal ones cannot readily be distinguished from those of 



L. proriger. 



Platecaepus latisplnis, Cope. 



The remains representing this species consist of seven cervical and 

 dorsal vertebrae; five of them being continuous and inclosed in a clay concre- 

 tion. It is a large species, nearly equaling the L. mitchillii in its dimensions, 

 that is, forty or fifty i'eet in length, and is intermediate between such gigantic 

 forms as Lioclon dyspelor and the lesser Platecarpi. The type-specimens were 

 found by Prof. B. F. Mudge, one mile southwest of Sheridan, near the "Gypsum 

 Buttes." These display the elongate character seen in Lioclon Icevis, &c; but 

 the articular surfaces are transversely oval, thus resembling the P. ictericua. 

 They are less depressed than in L. perlatus and L. dyspelor. The cup and 

 ball of the penultimate cervical are a little more transverse than those of the 

 fourth dorsal, and none of them are excavated above by the neural canal. The 

 last cervical is strongly keeled on the middle line below, and with a short, 

 obtuse hypapophysis marking the beginning of the posterior third of the 

 length ; the median line of the first dorsal has an obtuse ridge. There is no 

 keel on the fourth dorsal, but the lower surface is concave in the antero- 

 posterior direction. The diapophyses on the last two cervical and first three 

 dorsal vertebrae have great vertical extent; the articular surface for the rib 

 is not bent at right angles on the first dorsal. Neural arches and spines are 

 well preserved in most of the specimens. There is no trace of zygantrum. 

 The neural spines are flat, and have considerable antero-posterior extent on 

 cervical as well as dorsal vertebras, and are truncate above. The first dorsal 



bears a long, strong rib. 



Measurements. 



n. 



Transverse diameter of the cup of the penultimate cervical vertebra 0. 05 1 



Vertical diameter of the cup of the penultimate cervical vertebra 0. 041 



Length of the centrum of the fourth dorsal, without ball 0. 072 



Vertical diameter of the ball 0. 0455 



Transverse diameter of the ball 0. 0555 



Elevation of the front margin of the neural spine of the penultimate cervical 0. OSS 



Antero-posterior diameter of the neural spine of the penultimate cervical 0. 050 



There are smooth bands around the balls, and the surfaces of the centra 

 are striate to these. 



