ON ARCTOCEBUS CALABARENSIS 603 
In Galago minor the inner posterior cusp of the third upper molar 
is obsolete ; the oblique ridges of the lower molars are tolerably well 
marked, and the last has a fifth cusp. 
Otolicnus garneltit and O. crassicaudatus have the inner posterior 
cusps of the third upper molars rudimentary, the oblique ridges of 
the lower molars but little developed, and the fifth cusp of the third 
lower molar rudimentary. 
The upper molar teeth of the ordinary Lemurs (Varecia, Lemur, 
and Prosimia, Gray) have the inner posterior cusp obsolete, or very 
ScaleLENS 
Fic. 6. ‘ Fic. 7. 
Right molars and premolars of . Lemur Right molars and premolars of Lichanotus 
catta. tndre. 
A and C, upper; B and D, lower jaw. A and C, upper; B and D, lower jaw. 
small; and a very strongly developed cingulum, internally. The 
oblique ridges are sometimes present, sometimes obsolete. 
The lower molars have the oblique ridge and the anterior, basal 
process so developed as to assume, in some cases, a doubly crescentic 
or Rhinocerotic character (fig 6, D). 
In the Indri (fig. 7), lastly, there is a type of dentition which 
departs still further from that of Angwantibo. Of the upper five 
grinders, the two anterior are unicuspidate, and like the premolars of 
other Lemurs; the other three are quadricuspidate, the hindermost 
being the smallest. Each pair of cusps is united by a transverse 
ridge, and there is no oblique ridge. . . 
In the lower jaw, also, the first and second grinders are unicuspi- 
date, and premolar-like. The third has four cusps, connected in 
pairs by ridges, which are disposed obliquely from within outwards 
