SYSTEMATIC REVISION 



17 



Revised description: Skull unknown except for a fragment of a lower jaw. 

 Vertebrae small, resembling those of larger forms, but the lower face of the 

 centrum^ round from side to side instead of flat. The species is not clearly- 

 distinguished from limbatus or magnicornis, and can not be until the skull 

 is known. The appearance of small vertebrae of uniform size in Texas, 

 Oklahoma, and Illinois, without intermediate sizes connecting them with the 

 larger vertebrae, warrants holding this species as separate, provisionally. 



A V W \ \_/--^ / ./. 



P 



Fig. I. — Diplocaulus limbatus. ^t' \\_^ ^J— -.X^?^ 



A. Lower view showing the maxillary and palatine teeth. Ns^^^^S^/" 



No 4542 Am. Mus. X % 



B. Upper view of skull. No 4470 Am. Mus. Reduced. ^^^-5^~T^i>^ 



n, nasal; /, frontal; plf, post-frontal; /, jugal; sq, squa- 

 mosal; p, parietal; /ijy, prosquamosal; jo, supraoccipital plate; <, tabulare; /.lachrymal. 



Diplocajlus limbatus Cope. 

 Cope, Proc. Am. Phil. Soc, vol. xxx, 1896, p. 456. 



Type: An imperfect skull. No. 4471 Am. Mus. Nat. Hist. Cope Coll. 

 From Texas. 



Original description: "The character of the species is seen in the horns. 

 These are much less produced relatively to other regions than in the D. 

 magnicornis, and the postquadrate (quadratojugal) element is more distinct 

 and terminates in a separate apex below the principal horn. This tract, 

 which is fused with the principal bone in the D. magnicornis, is separated 

 from it by a groove in the D. limbatus, and the large fossa which it incloses 

 with the inferior side of the principal horn looks inward at an angle of 45°, 

 while it looks downward in the D. magnicornis. The terminal angle of the 

 post-quadrate (quadratojugal) body forms a prominent compressed offset, 

 rather than a free apex. In one specimen of large size it is inferolateral; in 

 type, entirely inferior. The principal horn is shorter and narrower than in 

 the D. magnicornis, and less divaricate. 



"As the mandibular rami are in place and their extremities are entire, 

 the length of the muzzle can be inferred. It is relatively longer and less 

 broadly rounded than in the D. magnicornis. The surfaces of the skull are 

 sculptured in a honeycomb pattern, as in the type species. 



" Measurements. 



mm 



"Length of the skull on median line 92 



Length of the skull to extremity of horn 220 



Width of skull at posterior border 160 



Width of base of horn 51 



Length from angle of mandible to end of horn 115 



Length from angle of mandible to postquadrate process 65 



Length of mandibular ramus 82 



Interorbital width (approximate) 20" 



2 



