546 Bulletin American Museum of Natural History [Vol. LXVI 



however, so very distinct that the smallest skulls show the character- 

 istic long, narrow basin of this species. 



The nasal process of the premaxilla of senegalensis covers the 

 anterior part of the nasal cavity surface of the orbital process of the 

 frontal to some extent, whereas in inunguis and manatus there is little 

 or no such covering, the upper border of the premaxilla lying below the 

 lower border of the frontal. This suture in senegalensis also differs from 

 the other species in being distinctly shorter, a configuration which is 

 accompanied by a relative rounding off of this end of the bone as con- 

 trasted with the sharply pointed ends found in adult manatus and inun- 

 guis. The specimen from the Congo does not, however, fit in with 

 Hartlaub's characterization of senegalensis as a manatee with the nasal 

 processes of the premaxillae distally expanded, for in this specimen these 

 processes show less terminal expansion than some Florida specimens of 

 the same size. 



The anterior frontal margin between the roots of the orbital process 

 in the African manatee is typically smooth and unserrated, but in this 

 character it does not diverge strongly from manatus in which, particularly 

 in old individuals, the frontal margin is a little jagged. The breadth of 

 this margin is, however, considerably greater in manatus than in sene- 

 galensis, and the combination of relative breadth and irregularity or 

 smoothness of this margin would probably suffice to identify any 

 specimen. 



The nasalia of manatees have been made known by Krauss and 

 Hartlaub, but the statements concerning them rest on an insecure footing 

 through the extreme variability in these bones and their frequent loss 

 in the course of museum preparation. Hartlaub concluded that the 

 senegalensis nasalia were typically platelike, that gradations to peglike 

 bones were not infrequent, and that it was possible that in some animals 

 these bones were completely undeveloped. The Congo Expedition 

 manatee possesses a very small and spongy left nasal bone, lightly fixed 

 in a small pit of the frontal. The nasal does not come nearer than 8 

 mm. to the ascending branch of the maxillary. There is but slight indica- 

 tion that the right nasal bone was ever present, though of course it may 

 have been present and free. 



The nasalia of manatus, as Hartlaub found, are typically thick 

 almond-shaped bodies, but his small series of four specimens does not 

 represent the range of variation, for I have found in a better series varia- 

 tion from large peglike bones to platelike types and have noted that in 

 some cases the nasalia do not seem to have been developed. Twelve 



