528 



ANATOMY OF VERTEBRATES. 



The thin borders of the ascending ramus diverge from the con- 

 dyle as they pass, the one downward and inward to the low angle, 

 and the other forward and upward to the better-marked and more 

 advanced coronoid, the obtuse end of which is nearer the last 

 molar than the condyle. A slight ridge above the angle bounds 

 the surface for muscular insertion behind ; and here the angle is 

 a little inflected. 



In the Woolly Lemur {Liclianotus laniger, fig. 177), the cranium 

 has a short paroccipital and a shorter mastoid process which 

 coalesces with the base of a large petro-tympanic bulla. The 

 squamosal is perforated by a venous foramen anterior to the 

 auditory meatus. The malar extends backward almost to the 

 glenoid cavity, which, as in follomng LemuridcB, is defended by 

 a posterior ridge. The large orbits reduce the intervening part 

 of the frontal to a narrow channel. The premaxillaries are 

 divided anteriorly by an angular cleft separating in the same 

 deecree the anterior or mid-incisors from each other. The lower 

 jaw is remarkable for the great production of its broad and 

 rounded angle : the back part of its symphysis is also produced. 



In Stenops gracilis, and especially in Tarsius spectrum, the 

 most remarkable feature in the cranium is the expanded frame of 

 the orbits, which are closely approximated above the nasal bones. 

 These overhang the premaxillaries, the most produced part of 

 which forms the lower boundary of the external nostril, from 

 which, in the Slender Lemur, the premaxillaries slope downward 

 and backward to the incisive alveoli. The temporal ridges are 

 widely separated along the upper part of the globular cranium, 

 where the coronal and fr on to-sagittal sutures intersect each other 



at right angles. As in the 

 Aye-aye and most Lemur- 

 idcB, the cranial sutures are 

 ' harmonias.' 



In the Slow Lemur (^Ste- 

 7iops tardigradus), the orbits 

 are less closely approximate 

 than in the Ste7iops gracilis, 

 and the anterior surface of 

 the small premaxillaries is 

 more nearly vertical. The 

 vomer divides the nostrils to their posterior apertures. 



In the Potto {Perodicticus, fig. 347), as in other Slow Lemurs 

 (Stenops), the cranial expansion behind the meatus auditorius 

 forms one-third the length of the skull, owing to the great pro- 



347 



Potto. LXIX* 



