430 CETACEA. 



The sex of each animal was thoroughly ascertained ; and in connection with the 

 two sexes I have to point out that, although the males, 6, 7, and 8, from the Hughli, 

 are fully adult, they are very much smaller in every way than adult females from 

 the same stream. The skeleton of the male No. 6 is 18-50 inches shorter than that 

 of the female No. 1. The great difPerence that exists between the size of their skulls 

 is well estahhshed by Plate XXXIX, in which fig. 1 is a representation of the male 

 skull and fig. 2 is that of the female skull, the two having been photographed toge- 

 ther. The skull of the female is 27*25 to 19*40 inches in the male, that is 7*85 

 inches longer. It will also be observed that the osseous snout of this female is pro- 

 portionally longer than the rostrum of the male, but both are about the same depth 

 at the middle, the depth of the conjoint jaws between the eighteenth and nineteeth 

 teeth is in the male 3-20 to 3*25 inches in the female at the same point. The 

 curvature of the snout is much the same in both, there being a considerable upturn- 

 ing of the extremity of the maxillaries and of the mandible. The trifling differences 

 observable between the form of the maxillary crests of figs. 1 and 2 (Nos. 6 and 1 of 

 tables) are of no importance, as these structures are variable ; and the outline of the 

 frontoparietal suture also differs considerably in different individuals of the same 

 sex, and even on opposite sides of the same skull. In all their essential features, 

 therefore, the male skulls, although much smaller, correspond to the female skulls, 

 but their teeth, although proportionally smaller than in the females, preserve the 

 same characters, their bases being much extended from before backwards and worn 

 flat. The male dolphins which I have tabulated, beyond being smaller and having 

 shorter snouts, show no other external features in which they differ from the females. 

 The question, however, suggests itself, are these differences to be regarded as specific 

 or merely as sexual ? I am disposed to adopt the latter alternative, but at the same 

 time, as still larger individuals are met with in the Ganges than any I have yet 

 mentioned, and mature females occur smaller than No. 1 of the accompanying 

 tables, my opinion on this point is not fully established. The skeletons Nos. 3 and 

 4 of these tables appear to be younger stages of the same specific form as No. 1, 

 with long slender jaws and the sharply pointed teeth of adolescence, but a difficulty 

 presents itself regarding the dolphin kindly forwarded to me by Mr. Clay, C.S., who 

 took great interest in this enquiry. (See Table I ? ^). 



This specimen was harpooned on the 23rd June 1867, near Meerpore on the Suraj 

 fork of the Bansi branch of the Ganges, about 10 miles north-west of Dacca, and 

 Mr. Clay forwarded to me a sketch of the animal in the flesh with the measurements 

 given in the accompanying table, along with the skeleton of the animal. Mr. Clay's 

 drawing corresponds essentially to my Plate XXV, figure 1 of P. gangetica, but the 

 teeth that remained in the jaw are represented as very large and much worn, indicat- 

 ing that the dolphin was considerably aged — a fact verified by the condition of the 

 skull and skeleton. By the time the skeleton reached me all the teeth had fallen out 

 of their sockets, the latter being well filled up with osseous deposit. The jaws, 

 although having much the same form and relative length to the rest of the skull as 

 in the female skull, Plate XXXIX, fig. 2, are much more feeble and have less depth, 



