1883.] t)ol [Cope. 



tlie length of the muzzle iii front of it, obliquely measured, and one-half the 

 distance from its posterior edge to that of the temporal roof (? squamosal 

 bone). Posterior outline of skull above, truncate, surface slightly convex 

 transversely. 



The premaxillary spines are short and wide, the nasals are also short and 

 wide. The prefrontals and postfrontals form the superior edge of the orbit, 

 excluding the frontals. The intercalaria (or ? pterotics) are very large; at 

 the externoposterior angle is a very small element in contact with the supi^- 

 occipital which may be the true intercalare. The supraoccipitals have 

 considerable transverse extent, running out externally in narrow apices. 

 All the bones of the cranium are sculptured in honeycomb fashion, the 

 ridges radiating on some of the bones. That is, on the posterior parts 

 of the frontals and parietals and anterior part of the intercalare and squa- 

 mosal. A groove follows the edge of the orbit, and turns inwards on the 

 prefrontal bone, forming a rudimental lyra. External surface of mandible 

 grooved below; superior part concealed. 



Measurements. M. 



Width of skull between posterior angles 018 



Interorbital width 008 



Axial length of skull 034 



" from muzzle to between centres of orbits. . .0096 



Width of muzzle at nares 0095 



Length from orbit to nostril 0035 



Depth of skull posteriorly, to mandible 010 



The superior part of the posterior region of the inner face of the dentary 

 bone supports a patch of small obtuse teeth, which narrows forwards into 

 the single row of the edge of the ramus. This patch is no doubt homolo- 

 gous with that which is so largely developed in Pantylus. 



The surface of the cranium has been mostly weathered away in the type 

 of Pariotichus, P. brachyops, and I suspect that it is really sculptured and 

 not smooth, as I originally stated. The P. megalops dilfers from the P. 

 brachyops in the larger orbit, the narrower interorbital space, and the 

 smaller and more numerous teeth. 



Pariotichus and Pantylus and probably Ectocynodon must be referred to 

 a special family, the Pariotichidm, which has teeth like the Edaphosauridm* 

 but differs from it in the entire overroofing of the temporal fossse. 



Chilonyx rapidens Cope, gen. uov. 



Char. Gen. — Teeth with the long diameter of the crowns transverse to 

 that of the jaws, and with the crown contracting to a single slightly in- 

 curved apex. Maxillary series of teeth short. Temporal fossae overroofed, 

 Superior surface of cranium divided into more or less swollen area by 

 grooves. 



The characters above enumerated indicate for this genus a position near 

 the DiadectidcB. From these it differs in the form of the teeth, and the 



* Proceed. Amer. Philos. Soc, 1882, p. 450. 



