THE FAMILIES AND GENERA. OF RATS. 
59 
In extent of distribution and in the number of its species Pteropus 
exceeds all other genera of Megachiroptera. It also has the most 
complete and least modified dentition. These two circumstances have 
caused the genus to be generally regarded as the most primitive of 
the group ; but it seems probable that the deflection and tubularity 
of the brain case, the great reduction of the audital bullse, and the 
complete absence of the tail are of more importance than the large 
number of teeth, and that Pteropus is in reality less primitive than 
Cynopterus , Rousettus , and Pterocyon. 
Genus ACERODON Jourdan. 
1837. Acerodon Jourdan, Ann. Sci. Nat., Paris, 2 e ser., VIII, Zool., p. 369 
( jubatus ). 
1878. Pteropus Dobson, Catal. Chiropt. Brit. Mus., p. 15 (part). 
1899. Acerodon Matschie, Flederm. des Berliner Mus. fiir Naturk., p. 9 (sub- 
genus of Pteropus. 
Type-species. — Pteropus juhatus Eschscholtz. 
Geographic distribution. — Eastern part of the Malayan region 
(Philippines, Djilolo, Batjan, Celebes, Flores, Timor, Sumba). 
Number of forms. — Seven or eight forms of Acerodon have been 
described. 
Characters. — Like Pteropus , but with smaller canines and larger, 
more complex molariform teeth. Dental formula as in Pteropus. 
Upper incisors as in Pteropus , but somewhat more elongate and less 
bluntly pointed. Lower incisors differing from those of Pteropus in 
the much greater contrast in size between the inner and outer tooth 
of each pair. Canines much shortened as compared with Pteropus , 
the mandibular canine little exceeding the height of pm 3 . Though 
reduced in length the canines retain their thickness, and the cingulum 
is even better developed than in the related genus. Small premolars 
as in Pteropus. Upper molariform teeth differing from those of 
Pteropus in relatively greater size, greater breadth of crowns, greater 
distinctness of cusps, and a peculiar trenchant character of the edges 
and ridges. First large lower premolar {pm 3 ) essentially as in 
Pteropus. The three succeeding teeth differ from those of all other 
Pteropidse in the presence of a broad, flat postero-internal heel, 
sharply differentiated from the two ridges and extending considerably 
beyond them, especially behind. Cranial and external characters as 
in Pteropus. 
Species examined. — Acerodon jubatus (Eschscholtz) and several 
undetermined forms. 
Remarks.— Although not generally recognized as distinct from 
Pteropus this genus is well characterized by the form of the lower 
cheek teeth. Additional characters are furnished by the reduced size 
of the canines and of the inner lower incisors. 
