202 



THE EXTINCT BATRACHIA, EEPTILIA 



Articular faces posterior cervical round or slightly depressed; hypapophysis very large; 

 surface everywhere sculptured striate; centrum long; small. L. congeops. 



Articular faces of all dorsals compressed, deeper than wide ; median line below, broadly 

 prominent. L - L.&VIS. 



LIODON PRORIGER, Cope. 



Macroimrut proriger, Cope, Proceed. Ac. Nat. Sci., Phil., 1800, p. 188. Hujus operis Tub. XII, rigs. 22-24. 

 Leidy, Cretac. Kept. 11, 15-16 (caudal vertebra). 



The history of this large Mosasauroid is based on material in the Museum Comparative Zoology, Cambridge, Mass., 

 brought by Prof. Louis Agassiz from the cretaceous beds in the neighborhood of Fort Hayes, Kansas, and near the 

 line of the Southern Pacific Railroad. It consists of the greater part of the muzzle from the orbits, with the rightden- 

 tary and left pterygoid bones nearly complete! one cervical vertebra (with hypapophysis), one dorsal, one caudal with 

 diapophysis, and ten caudals without diapophysis. 



The characters presented by the vertebral column Indicate an excessively elongate reptile; the transverse diameter 

 of one of the distal caudal vertebrae is less than one-fifth that of a. proximal with short diapophysis; while four consecu- 

 tive ones of the former show but little variation in dimensions. This diminution amounts to j of a. transverse diameter 

 of the larger form. Willi this ratio as a, basis, fifty-three § vertebrae would form a, complete series from caudals one- 

 half the diameter of the last, of the four, to I he proximal caudal above mentioned. There have been, no doubt, several 



caudals in advance of the tetter, as the diapophyses are small. From the slow rate Of diminution of the columns of 

 other species examined, it, may be supposed that sixty caudal vertebrae is below rather than above the true number. 



The cervical and dorsal vertebrae have been slightly crushed as they laid on the side, and present, a, narrower diam- 

 eter than is normal; the cup of the cervical has not been distorted, and is deeper than wide, presenting the! character 

 of Macrosauras. The rudimental zygosphen consists of a continual ion of the roof of the neural canal in front, toadapl 

 itself to the inner dice of the down-looking zygapophysis of the preceding vertebra. Thi! latter is thus received into 

 a, groove on the inner side of the up-looking posterior zygapophysis. The dorsals and caudals exhibit with the cervicals 

 that minute, sharply defined rugosity, which characterizes all the; projecting margins, especially those of the hypapo- 

 physis and diapophyses, in this genus and Clidastes. The whole surface! of the cervical is marked will) either inoscu- 

 lating stria; or impressed punctae. The; same character marks the' cranial bones, though they elej not, present such ru- 

 gosity as the; vertebrae. 



The proximal caudal presents a subhexagonal section, of which the inferior add supero-lateral sides are longest; 

 articular faces about as broad as high. A broad smooth space between the chevron bones. Diapophyses with broad 

 ovate transverse section. 



A caudal without diapophyses, anterior to the middle of the series, estimated by the size, is but slightly deeper 

 than long, and with parallel lateral outlines of the articular faces. The neural arch is very much narrowed antero- 

 posteriorly, but, has a greater transverse extent at its lower part; above the' spine is much oompressed, but not widened. 



The; zygapophyses remain as rudiments just above the small neural canaj but, el >t probably touch each other. There 



are twee anterior and twee posterior narrow ribs on the upper portion of the; neural spine'. 'Hie; more distal caudals have 

 wider neural spines, anil the' aroh also has a, greater anteroposterior extent. The zygapophyses are scarcely traceable 

 ami the neural spine is strongly striate. The; reverse arrangement is observed in Clidastes propython, where the neu- 

 ral spine; of the proximal caudal has considerable extent, while those of the posterior and distal vertebrae are almost, 

 cylindric, especially the neurapophyses. 



Dimensions. * n - 



Dorsal, length, 8.85 



" width eaip, »■>> 



" depth " 2.77 



Proximal caudal, length, 2.14 



.■; 



