1934] Hatt, African Manatees 541 



bore 18 pairs of ribs according to Jentink, 1888, p. 33) seems then to be 

 in line with this form, being more nearly allied to the species manatus 

 than inunguis. The numbers of lumbo-caudal vertebrae vary in the 

 same Florida specimens from 27 to 29 (without respect to the number 

 of rib-bearing elements in the same skeleton) . In the Puerto Rican and 

 Congo specimens there are 25 lumbo-caudals. Twenty-six were found in 

 Buttikofer's Liberian manatee (Jentink, loc. cit). In the two Amazonian 

 specimens there are 25 (older) and 22 (younger). 



Other than this variation in numbers, in which specific tendencies 

 seem to be weakly manifest, no characters of the column show any 

 constant differences between the forms. 



The Sternum 



The sterna of manatees present well-marked shapes that, though 

 individually variable, are specifically constant in certain features. 



The sternum of senegalensis is much like that of manatus, except 

 that the African species does not (in the Congo specimen ) have a deep 

 median notch in the anterior border of the bone but may have two 

 light notches flanking a median prominence. This difference may be 

 clearly seen by an examination of figure 1. The margin of the caudal 

 prolongation of the sternum in the Congo specimen is also incised, a 

 condition uncommon in the species manatus. 



The sternum of inunguis is a smaller bone in proportion to the 

 size of the animal than that of manatus and senegalensis and may be 

 recognized by its slender proportions and backwardly directed lateral 

 processes. 



The Appendicular Skeleton 



The Pectoral Girdle. — The pectoral girdles of manatees differ in 

 the proportions of their component parts, but there is no deviation from 

 the essential form. As in most other characters, the South American river 

 manatees differ most widely from the type species manatus, for their 

 flippers are proportionately longer than those of the other members of 

 the genus, a lengthening which has occurred chiefly in the metacarpals 

 and phalanges. 



The scapula (Fig. 2) of the Congo manatee more closely resembles 

 that of inunguis than that of manatus. From both it differs in being 

 comparatively long and narrow and in having the coracoid border gently 

 curved and without a pronounced angle at the coraco-vertebral juncture 

 or above the incisura. The spine is apparently a little higher, the 



