SYSTEMATIC REVISION 45 



wide above in proportion to its length. It is probable that the width of the skull 

 behind does not exceed the length from the posterior border to the front of the 

 orbit, though this measurement is uncertain, owing to the mutilated condition of 

 the right side. 



"The surface is sculptured with shallow pits separated by rather thick ridges. 

 The nasal bones send back a short angle of the external margin to meet the inferior 

 prefrontal suture, about half-way between the orbit and the nostril. 



"Measurements. 



"Length of skull to the end of OS quadratum 0-054 



Length of skull posterior to orbit 018 



Length of orbit 015 



Length from orbit to nostril 012 



Width of muzzle at middle 105 



Width of the interorbital space 010 



Width of the intemarial space .008 



Length of the recurved part of the premaxillary 007 



Length of premaxillary I, I 005 



Length of the longest premaxillary tooth 00+ 



Depth of mandible at middle of orbit 006" 



Revised description: The median pair of upper incisors are abruptly larger than 

 the second, but not so much so as in aguti. The fifth maxillary tooth is abruptly 

 larger than those before it, the sixth and seventh smaller than the fifth but larger 

 than those which follow. The position of the premaxillary bones and the lower jaw 

 in the type specimen is evidently due to crushing which pushed the lower part of 

 the skull backward with reference to the upper. The sculpture of the surface is 

 not to be distinguished from that of the other species. The proportions of the 

 skull and the orbits are not to be trusted as they would be in recent skulls, for all 

 have suffered more or less from crushing and every specimen would show variations 

 in the diameters of the orbits, the interorbital width, and length of the skull. The 

 three mandibular incisors are enlarged, as in all the species. 



Genus LABIDOSAURUS Cope. (Plate 12.) 



Partotiehus Cope, Proc. Am. Phil. Soc., vol. xxxiv, 1896, p. 448. 

 LabiJosaurus Cope, Proc. Am. Phil. Soc., vol. xxxv, 1896, p. 136. 

 Pariottchus Case, Zoolog. Bull. vol. 11, 1899, p. 231. 

 LabiJosaurus Broili, Paleontographica, Ed. 11, 1904, p. 51. 

 Labtdosaurus "Williston, Jnl. Geol., vol. xvi, 1908, p. 395. 



Type: A skull with the lower jaw. No. 4341 Am. Mus. Nat. Hist. Cope Coll. 

 From Texas. 



Original description: "One series of pleurodont maxillary teeth slightly un- 

 equal in size. Internal incisor much enlarged, conic, acute, and directed backwards. 

 No teeth on the maxillopalatines; teeth on the palatines small, subconic, in one row. 

 Nostrils lateral. Better specimens of the above species (P. hamatus) show that it 

 has but one row of maxillary teeth, which are pleurodont, so that it is clearly a 

 member of a genus distinct from Pariotichus. If the character which I have 

 assigned as definitive of the Pariotichida be the true one, the genus Labidosaurus 

 must be referred to a different one, and I know of no character at present to separate 

 it from the Pariasaurida of which the known species are, so far as known up to the 

 present time, restricted to South Africa. It differs from the known genera of that 

 family in the greatly elongate premaxillary teeth, and in the simple conic dental 

 crowns." 



