GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



167 



Pterygoids 

 Text Fig. 58 



Although the sutural Hmits of these elements are ill defined, it is evident that they articulated ante- 

 riorly with the vertical plate of the palatine and covered the inner side of the descending plate of the 

 alisphenoid, against which they were tightly appressed, the pterygoid fossse being only small slits between 

 the lower border of the true pterygoids and of the alisphenoid; in Adapts, on the contrary, the pterygoids 

 are separated below from the alisphenoids by a wide pterygoid fossa, the large size of which was doubt- 

 less correlated with the expansion of the fossa for the insertion of the internal pterygoid muscle on the 

 medial surface of the angle of the mandible. The hamular process of the pterygoid is broken off near the 

 base, but it evidently extended backward in the normal lemuroid manner. The hamular process is 

 continuous above with a low ridge which runs posterodorsally along the inner side of the pterygoid. No 

 such ridge is shown in Adapts. 



Palatine 

 Text Fig. .58 



But little of the horizontal plate of the palatine is preserved; the palato-maxillary suture extended 

 forward to near the posterior part of m^ (Amer. Mus. No. 11466, 12569); the palate was narrower than 

 in Adapts parisiensis and the horizontal plates of the palatines were probably even narrower than in the 

 primitive Adapts tnagnus var. leenhardti. The position of the posterior palatine grooves and foramina 

 and the characters of the posterior palatine ridges are not known. The vertical plate of the palatine 

 is preserved in the type of N. oshorni; its stout lower rim as in Adapts was separated from the alveolar 

 region of the maxillary by a notch for the posterior palatine artery, as in Adapts (cf. Stehlin, 1912, p. 

 1202) and Coenopithecus, while in modern later Primates this notch, which becomes more or less united 

 with the true posterior palatine foramen, is closed by the union of the palatine and maxillary below it. 

 The inner surface of the ''vertical" plate of the palatine slopes obliquely inward and upward toward 

 the presphenoid ; it bears a prominent convex ridge running posterointernally and slightly dorsally toward 

 the midline, where with its fellow of the opposite side it joins the median ridge of the basisphenoid 

 described above (p. 166). Anterointernal to this ridge the basicranial floor was gently concave, on 

 either side of the midline. Here were the posterosuperior limits of the internal nares. In Adapts 

 this region appears to be wide and flat. The palatine was in contact with the pterygoid, the pterygoid 

 and temporal plates of the alisphenoid, the maxillary, the lacrymal, the frontal and the orbitosphenoid, 

 but the sutures separating it from these elements are not visible. The vertical plate of the palatine 

 passes dorsosuperiorly into the large orbital plate which overlaps the descending wall of the frontal. 

 The contact with the lacrymal is not shown. This is pierced by the sphenopalatine foramen (for the 

 nerve of the same name) and from this a groove leads back toward the foramen rotundum or foramen 

 lacerum anterius, whichever it may be. The limits of the orbitosphenoid and of the orbital part of 

 the alisphenoid are not visible. The foramina at the back of the orbit are poorly shown. 



Brain Cast 

 Text Fig. 63 



A natural cast of the cranial cavity is partly exposed in Nothardus tyranmis, Amer. Mus. No. 11478. 

 It affords a general but imperfect outline of the brain-cavity as seen from above. Certain details of the 



