1-27 



December 13. 1836. 



Richard Owen, Esq., in the Chair. 



Part of a paper by M. Frederick Cuvier was read, on the Family 

 of the Dipodida, including the Jerboas and Gerbillas*. 



Mr. F. Debell Bennett, Corresponding Member of the Society, 

 then read some Notes on the anatomy of the Spermaceti Whale, 

 {Physeter macrocephalus, Auctorum,) principally relating to its den- 

 tition, and to the struclure and appearances presented by the soft 

 parts. 



Mr. Bennett remarks that a greater disproportion exists between 

 the sexes in this species of Whale than is observed in any other 

 cetaceous animal ; for while the usual length of the largest male 

 Cachalots, taken in the Soutfi Seas, is about 60 feet, that of full- 

 grown females is only 28, and rarely, if ever, exceeding 35. 



When the young male Cachalot has attained the length of 34 feet, 

 its teeth are perfectly formed, though not visible until it exceeds 28. 

 The upper jaw usually described as toothless, has on either side a 

 short row of teeth, sometimes occupying the bottom of the cavities 

 which receive the teeth of the lower-jaw, but generally corresponding 

 to the intervals between them. The entire length of these teeth is 

 about three inclies ; they are slightly curved backwards, and elevated 

 about half an inch above the soft parts, in which they are deeply 

 imbedded, having only a slight attachment to the maxillary bone. 

 Their number is not readily ascertained, because the whole series are 

 not always apparent ; but in two instances Mr. Bennett found 8 on 

 each side. These teeth exist in adult Whales of both sexes, and 

 though not visible externally in the young Cachalots, may be seen 

 upon the removal of the soft parts from the interior of the jaw. 



" The eye of the Cachalot is small, and placed far back on the head, 

 above and between the pectoral fin and angle of the lower jaw. Its 

 situation is chiefly marked by a raised portion of integument around 

 it. Tlie aperture for visicm does not exceed 2 inches in the longitu- 

 dinal, and 1 inch in the vertical direction. The eyelids are without 

 cilia and tarsal cartilages ; they are composed of two horizontal bands 

 of integument, each, in the example from which I describe (viz. a half- 

 grown male), two inches in depth, and connected with each other at 

 the inner and outer canthus. Between each of the eyelids and the 

 blubber exists a distinct line of separation, marked by a somewhat 

 deep groove, having a duplicature of thin membrane, serving as a 

 surface or hinge on which the lids move. At these lines of demar- 

 cation all integument partaking of the nature of fat ceases, and the 

 texture of the tarsi thus insulated is composed solely of common 

 skin and cellular and other membranes, together with a dense layer 



• The abstract of this and the concluding part of thn Memoir will be 

 foiuul in the Proceedings for IJecenibev 27, 1836. 



No. XLVIII. PaOCEKDINGS OK THE ZoOLOfiUAL SoClETY. 



