CHAP. IV] THE GENERAL ANATOMY OF THE LEMUROIDEA 73 



A general survey of the palmar and plantar surfaces leads 

 to the conclusion that the Lemurs represent a stage in the 

 evolution of a more highly-developed type. In the latter the 

 surfaces in question are more completely covered by epidermis 

 marked with continuous figurae tactiles. Yet the Lemurs them- 

 selves are relatively elevated in comparison with most of the 

 Eutherian mammals other than the Primates. We may regard 

 the extent and moulding of the surfaces thus modified as indices 

 of progressive specialization in the employment and interpre- 

 tation of tactile stimuli. The psychological significance of these 

 morphological characters is thus seen to enhance their value in 

 elucidating the biological relations of the several representatives 

 of the Primates in which they are here described. 



E. The Skeleton. The skull (Fig. 41) is elongated, the brain- 

 case being somewhat flattened, and the facial bones project as 



Paneto- sphenoid 

 articulation 



Ethmoid bone 



Lachrymal bone 



Auditory 

 bulla 



Cdntnif orm. 



premolar 



tooth 



nasi form, 

 canine tooth 



Fig. 41. Cranium, with mandible, of Lemur varius ; note the auditory bulla, 

 the articulation of parietal and alisphenoid bones, the facial extension of the lachry- 

 mal bone (cf. Fig. 21), the articulation of the frontal bone and maxilla behind the 

 lachrymal bone, the small forward projection of the orbital plate of the ethmoid 

 bone, the number of teeth, the small size of the upper and the great projection of 

 the lower incisor teeth. In the mandible, the canine-like tooth is a pre-molar by 

 position, and the canine tooth is incisiform. 



a snout, at the extremity of which is the aperture of the nose. 

 On the inner orbital wall, the frontal and maxillary bones join 

 along a suture for a distance of about 5 mm., and thus widely 

 separate the ethmoid from the lachrymal bone. The infraorbital 

 nerve is provided with a groove not covered in to form a canal. 



