282 Prof. Eschricht on the Gangetic Dolphin. 



mity in the crania reappears in the connexion of the pars petrosa 

 with the bulla tympani, and still more its protrusion into the 

 walls of the skull and peculiar connexion with the temporal bone. 

 But here a still greater similarity presents itself with the Cacha- 

 lot, which is far more closely allied to the Hyperoodons, than any 

 other Linnsean dolphins. In the form of the under jaw it is more 

 like the Cachalot ; while in that of the upper jaw, it resembles 

 most the Hyperoodon. Its great supply of teeth must have ap- 

 peared a strong objection to earlier observers, to consider it as 

 nearly allied to the Hyperoodon and Cachalot, in the former of 

 which the teeth exist only in the most anterior part of the under 

 jaw, and in the latter they are confined entirely to the lower jaw. 

 This objection, however, has lost the greatest part of its force, 

 for I have succeeded in proving, that there exists a complete 

 series of teeth in both jaws of the Hyperoodon, though they 

 never attain their full development (/. c. pp. 375 and 337). 

 There is, at least, this similarity of teeth ' between the Hyper- 

 oodon and our dolphin, that the foremost are by far the most de- 

 veloped, which is not the case in any of the dolphins proper ; 

 and between it and the Cachalot, and the Hypei'oodons generally, 

 that they are most developed in the under jaw, though compa- 

 ratively in a very slight degree here. This undeniable analogy 

 in the structure of the cranium, with the Hyperoodons, and 

 partly the Cachalot, which is not far removed from these, is alto- 

 gether lost almost, as regards the rest of the skeleton. 



In the skeleton of the Hyperoodon we have the following 

 striking peculiarities : — 1. a most unusually low number of ribs 

 (9 pairs for 55 vertebrae) ; the thorax close up to the heavy head ; 

 all the seven vertebrae of the neck grown together into one mass 

 of bone ; 2. the strikingly extended lumbar region, as compared 

 to the neck and thorax, considerably longer than both these 

 together, and almost as long as the tail; and, 3. the not less 

 strikingly high and bulky spinous processes. On the contrary, 

 in the Gangetic dolphin we see — I. a very usual number of ribs 

 (11 pairs to 51 vertebrae) ; the thorax removed to an unusually 

 great distance (for the order of whales) from the head, owing to 

 the length of the neck (only 11|^ times shorter than the entire 

 vertebral column, in the Hyperoodon about 28 times), and the 

 cervical vertebrae being, besides, strongly developed, and moveable 

 among themselves ; 2. the lumbar region only somewhat more 

 than double the length of the neck (y^y), exactly the length only 

 of the thorax, and only about | (^§J) of the tail ; and finally, 

 3. the spinous processes short, not only in comparison with the 

 Hyperoodons, but generally with dolphins proper. All these 

 discrepancies indicate a great diversity in the mode of living of the 

 Gangetic dolphin and the Hyperoodon. The skeleton of the last 



