xvi.J CETACEA. 303 



any excessive number of phalanges. In the Grampus (Orca) 

 all the phalanges are broader than they are long. 1 In the 

 round-headed Dolphins (Globicephalus, Fig. 105), on the 

 other hand, the manus is extremely elongated, narrow, and 

 pointed. This elongation is mainly due to the great develop- 

 ment of the second, and, though to a less extent, of the 

 third digit ; the fourth and fifth being quite short, and 

 having but few phalanges. The number of phalanges (in- 

 cluding the metacarpals) in the different digits are respec- 

 tively I. 4, II. 14, III. 9, IV. 3, and V. i. 



In the common Dolphin (Delphinus) the manus has the 

 same essential form, though in a less exaggerated degree, 

 the numbers of the phalanges being I. 2, II. 10, III. 7, 

 IV. 3, and V. i. The digits are all in close contact. 



Order SIRENIA. Though in external form, and in being 

 inclosed in an undivided integument, the terminal segment of 

 the fore limb of the animals constituting this order much 

 resembles that of the Cetacea, its skeleton is totally different. 



The carpus is short and broad. In the genus Manatus 

 the seven most usual bones of this region are all distinct, 

 though there is no pisiform. The trapezoid is very small 

 and placed almost on the dorsal surface of the trapezium. 

 The cuneiform is large, and supports the greater part of the 

 fifth metacarpal. In Halicore many of the bones of the 

 carpus usually coalesce ; thus the first row may consist of 

 two bones, a scapho-lunar and a cuneiform, and all the 

 bones of the second row rr.ay unite together. 



In both genera the digits are five in number, with 

 moderately elongated and flattened phalanges, which are 

 never increased in number beyond the limit usual in the 

 Mammalia. 



1 This genus is remarkable for the imperfect ossification of the carpal 

 bones. 



