268 



PEIMATES 



The Prosimia are separated into six families : Adapidae, Anaptomorphidae, 

 Tarsiidae, Lemuridae, Chiromyidae and Galeopithecidae. The first two occur 

 only in the older Tertiary ; Europe and North America. Several genera of 

 the true lemurs are known from the Pleistocene of Madagascar. The last two 

 families belong exclusively to the Recent. 



Familv 1. Adapidae Tronessart. 



Dental formula . 



2.1.4.3. 



Dental series continuous above and below. Incisors 



2.1.4.3. 



and canines normal. Superior' molars tri- or quadriiubercular, protocone large, 

 V-shaped ; hypocone small. Lachrymal foramen at the anterior border of the orbit. 

 Humerus with entepicondylar foramen. Tarsus not elongated. Fossil in the 

 Eocene ; Europe and North America. 



The skulls of Adapis (Fig. 355) and Notharctus are characterised by 

 a high sagittal crest and relatively small orbits, beyond which the facial 



portion is much constricted. The elongated 

 muzzle with its long narrow nasal bones, the 

 completely closed orbits, and the position of 

 the lachrymal foramen are all distinctive of the 

 lemurs. In many forms, however, the two rami 

 of the mandible are anchylosed at the symphysis, 

 while the ascending branch is characterised by 

 considerable breadth and depth, and there is 

 usually a process on the posterior border. Two 

 or three small foramina are found below the 

 anterior premolar. The large greatly inflated 

 auditory bullae, which diminish anteriorly, also 

 recall the Lemuridae. In the anterior portion, 

 at least, the dentition approaches more nearly 

 that of the true apes, especially the American 

 apes, than that of the lemurs. In other respects 

 it is characterised on the whole by indifferent 

 primitive characters. Although they possess a 

 quadritubercular crown, the tritubercular type 

 may still be distinctly recognised in the superior 

 molars, for the small postero-internal column (hypocone) always appears as an 

 accessoiy tubercle. The quinquetubercular or quadritubercular inferior 

 molars show no marked differentiation, and could as well pertain to primitive 

 ungulates or creodonts as to the lemurs. In comparison with those of 

 apes and lemurs, the premolars are fully developed and, with the exception of 

 the most anterior, are single rooted and monocuspid, with an internal tubercle 

 above and a talon below. In the mandible, the fourth premolar is often 

 like the first molar, while the last superior premolar reaches at the most the 

 tritubercular stage. The posterior milk cheek tooth in both jaws agrees 

 with the anterior true molar. The canines above and below are conical, 

 tapering, somewhat decurved, and have the same structure as in all primitive 

 ungulates, insectivores, carnivores, and apes, but not as in the existing lemurs. 

 The development of a third pair of incfisors in Hyopsodus, however, also here 



■A, 



Fig. 354. 

 Pelycodus tutus 



Cope. 



Lower 

 Eocene (Wasatch beds), Wyoming. Left 

 upper jaw, palatal aspect, i/i. B, C, 

 Pelycodus/rugivorus Cope. Hid. Lower 

 jaw, upper and outer aspects. Vi- 

 (After Cope.) 



