1934] Hatt, African Manatees 545 



senegalensis and manatus being essentially short-fingered and inunguis 

 long-fingered. 



The Pelvic Girdle. — The immaturity of our Congo manatee 

 precludes the determination of specific characters which might appear in 

 the innominate bones, but these bones are sufficiently developed to 

 furnish a key to the sex of the specimen and show it to be a female. 

 These bones are indistinguishable from those of immature female Florida 

 manatees and from those of certain Surinam specimens figured by Krauss. 

 My failure to find any innominate bones in two uncleaned inunguis 

 skeletons fresh from the field, and the lack of mention or figuration of 

 these bones in literature may indicate that this species has completely 

 lost its pelvic girdle. 



The Skull 



A glance serves to identify the skull of Trichechus inunguis, but the 

 differences between the skulls of senegalensis and manatus are more 

 subtle. The two manatees last mentioned differ from inunguis, not only 

 in the general shape of the skulls, but in the very character of the bone 

 itself, for though the skull bones of senegalensis and manatus are in general 

 dense and smooth, those of inunguis are, with rare exceptions, soft, 

 chalky, and rather elaborately roughened. The skull bones of this latter 

 species are also lighter in proportion than those of the other two. 



The general skull shape of senegalensis and manatus is broad and 

 compact and the snout short (senegalensis being shorter than manatus 

 in this respect), whereas the skull of inunguis is lengthened and char- 

 acterized by a long snout. The conspicuous recession of the nasals and 

 the posterior border of the anterior nasal opening leaves at the anterior 

 end of the skull the characteristic large nasal basin, the floor of which is 

 formed by the palatal parts of the maxillae and the vomer. The form of 

 this basin is dependent in the main upon the extentof the forward growth 

 of the premaxillae, and this is a process progressing with age to maturity, 

 or possibly throughout life ; but when comparisons are made of skulls of 

 equal length, specific patterns are discernible. This nasal basin is 

 broader in the adult African manatee than the corresponding area in 

 manatus, but the difference is very slight, and in immature specimens it is 

 impossible to distinguish these two species on the basis of this feature. 

 The adult manatees of the western Caribbean and Gulf of Mexico appear 

 to be slightly longer snouted than corresponding specimens from Florida, 

 but additional material would be necessary to establish the constancy of 

 this probable difference. The nasal basin of the Amazonian manatee is, 



