258 THE MERYCOIDODONTIME 



The temporal ridges unite just back of the postorbital constriction and form a high, narrow sagittal 

 crest, a little more than a third of the skull length. There is an apparent foramen, produced by the 

 spreading of the parietal bones and about on a line with the paramastoids, situated a little abaft the 

 mid-length of the sagittal crest. It does not appear to be a real foramen, as the walls seem to come 

 together a little way below the aperture. It looks like a normal condition in the living animal and 

 not like a postmortem wound. What its function may have been can only be guessed. The supra- 

 occipital crest extends backward at about a 45° angle on each side but probably did not extend 

 beyond a line above the occipital condyles. There is a deep concavity on either side of the occipital 

 pillar. 



The brain case is relatively large, with a ridge along the parietosquamosal suture and another, 

 nearly paralleling it, making a shoulder on the anterior sides of the brain case. The external 

 auditory meatus is large and for the most part posteriorly directed, although it has also a slightly 

 outward direction. The palate is wide and nearly flat, and the palatonarial border, U-shaped, 

 advances to a line through the middle of the last molars. The basicranial axis has a slight slope. 

 The glenoid surface is nearly flat. The whole basicranial region is extremely foreshortened, so that 

 the much-inflated bulla; lie below a part of the glenoid articular surface, and their anterior border 

 is in advance of that surface. These bulla; are oval in outline, with their long diameter directed 

 forward and inward at a slight angle. This foreshortening of the basicranial area does not occur so 

 markedly in the more normal forms of Cyclopidius. The postglenoid processes are small, thin and 

 plate-like, situated almost directly above the posterior margin of the bulls. The tympanic abuts 

 against the postglenoid and seems to be a part of it. The paroccipital process is transversely wide 

 at the base, closely appressed against the bulla, then extending freely, with a diamond-shaped cross 

 section. Index: 0.81. 



Foramina: The infraorbital lies above the interval between P 3 and P\ The supraorbital 

 foramina are small, farther forward from the temporal ridge than in Cyclopidius, and roughly mid- 

 way of each side of the median line. Far back, above the anterointernal part of the bulla, lies a 

 small foramen lacerum medium, a large foramen ovale, and what appears to be a small foramen 

 rotundum, while considerably in advance, in its normal position, is a large foramen lacerum anterius. 

 Cope mentioned a large foramen rotundum in C. emydinus = ?C. simus. I have not been able to 

 ascertain whether the foramen rotundum is characteristically present or not. It appears to be present 

 also in Leptauchenia. This is rather remarkable in that in most of the contemporary genera its 

 absence is noteworthy. However, Cyclopidius is primitive likewise in having five toes on the 

 manus. 



Dentition: The teeth are hypsodont, and the styles are better developed progressively from 

 front to back in the molar series, those of M 1 not being especially prominent. The metastyle of M 3 

 is not well developed. The molars fall in the broad-toothed type, and their general construction 

 follows that of this group, the index of M 1 being 1.21, while the molar-premolar index is 0.70. 

 The premolars are crowded but do not overlap, and the canine is somewhat oval in section antero- 

 posteriorly. The tooth rows converge from back to front more markedly than is usual in 

 Cyclopidius. 



