368 CETACEA. 



Humerus, 8fC. — The humerus, radius, and ulna (Plate XLII, fig. 9), do not 

 call for special remark, as they have the characters generally presented by these 

 bones in Orca, to the limb of which the limb of Orcella as a whole has a strong 

 resemblance. Including the metacarpals the following numbers are distinctive of 

 Orcella fluminalis : I, 2 ; II, 8 ; III, 6 ; IV, 3 ; the fifth finger is reduced to a 

 cartilaginous rudiment with a bone at its base which appears to be the metacarpal 

 of the digit, the bone internal to it being the cuneiform. Thus there are only five 

 carpal bones consisting of two rows, three bones to the proximal and two to the 

 distal row. They are largely imbedded in cartilage, and widely separated from 

 each other. 



Conclusion.— The facts here adduced are sufficient to establish the existence of 

 two distinct species of small round-headed dolphins, one marine and the other 

 fluviatile. The details of structure yet to be given under Orcella brevirostris, 

 Owen, will clearly show that they are entitled to generic rank. 



