155 



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



from a bliiti' on Butte Creek, belongs perhaps to this species. Tiic proximal 



specimens, at least, cannot he distinguished from those of Professor Mudge's 



collection. Tiie distal ones cannot readily be distinguished from tiiose of 



L. proriger. 



Platecakpus latispinis, Cope. 



The remains representing this species consist of seven cervical and 

 dorsal vertebra^; live of them being continuous and inclosed in a clay concre- 

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

 that is, forty or Hfty feet in length, and is intermediate between such gigantic 

 forms as hiodon dijqjelor 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 Liodon hevi.t, &c. ; l)ut 

 the articular surfaces are transversely oval, thus resembling tlie P. iderkus. 

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

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

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

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

 obtuse hypapophysis marking the beginning of the posterior third of tlie 

 length ; the median line of the first dorsal has an obtuse ridge. There is uo 

 keel on the fourth dorsal, but the lower surtace 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 lor the rib 

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

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

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

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



bears a long, strong ril). 



Mcasurement>i. 



ji. 



TrauBvcise diameter ol the cuji of the penultimate cervical vertebra 0. 0.")! 



Vertical diameter of tLe cup of the pemiltinuite cervical vertebra 0. (Ml 



Leugth of the centrum of the fourth dorsal, without ball (i. UT'J 



Vertical diameter of the ball 0. 0-l>=)5 



Transverse diameter of tlie ball 0. 0D.")5 



Elevation of the front margin of tin' neural spino of the penultimate cervical 0. OSJJ 



Anteroposterior diameter of tin; 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. 



