Vol. 56.] DICRANOZYGOMA LEPfOSCELUS. 647 



In its absence some uncertainty attaches to the determination of 

 the affinities of the animal, although enough of the skull remains to 

 show that there are striking features which separate it from all known 

 genera of Theriodontia. It is one of the most important skeletons 

 hitherto found, and is unique in the evidence which it affords of 

 coordination of characters of the dorsal aspect of the more interest- 

 ing bones. 



The Head. 



The skull appears to have been about 4j inches long in the 

 median line; but its greatest length was about 6 inches, owing to 

 the unusual expansion and backward lateral prolongation of the 

 squamosal bones. The greatest width of the skull transversely was 

 in the line of the vertical occipital plate, where the measurement 

 from side to side exceeds 4| inches. 



The inner borders of the orbits of the eyes are concave in 

 length, and the least width of the interspace between them exceeds 

 1 inch. The hinder lateral border formed by the postfrontal bone 

 is preserved on the leftside, and has a thickened rounded prominent 

 edge. This triangular bone, narrowing as it extends outward, is 

 concave between its prominent anterior and posterior margins, and 

 makes the anterior limit of the short and wide temporal vacuity. 

 The transverse measurement of the postfrontal is about J inch. 

 Its narrow outer edge is directed downward towards the malar 

 region. The space between the postfrontal bones, occupied by the 

 frontal bones, is slightly convex, and is traversed by short elevated 

 longitudinal ridges, which are not parallel but meet so as to enclose 

 long, shallow, fusiform pits, seven or eight in number, in the trans- 

 verse width of the bones. This ornament is extended backward 

 upon the parietal region; but there is no evidence of it farther 

 forward, because the front of the head is in the missing part of the 

 specimen. This Labyrinthodont type of ornament is known in 

 certain skulls of Theriodonts, but is unknown in Oudenodon, 

 Dicynodon, or any other South African reptiles with which this 

 fossil may be compared. I have not seen, however, the same net-like 

 pattern in Cyiiognathus, or any Theriodont hitherto described. 

 Behind the postfrontal bones the short parietal region of the skull 

 has slightly concave sides with sharp edges which converge some- 

 what as they extend backward. The parietal foramen is longitu- 

 dinally oblong, and about 1 inch in advance of the occipital plate. 

 Immediately behind it the surface of the parietal bones becomes 

 concave. 



The occipital plate is nearly vertical, and subtriangular, 

 \ inch wide at the apex, at the median superior crest of the occiput. 

 This region widens with a narrow concave lateral margin, which 

 excavates a deep wide notch between this triangular plate of the 

 skull and the lateral expansion of the squamosal bone, corresponding 

 to the condition of the narrow edge in the triangular occipital plate 

 of Gomphognathus, and corresponding to the deep lateral V-shaped 

 notch seen in that genus between that plate and the squamosal 

 region of the zygomatic arch. The width of the base of the occipital 



