127 



December 13. 183G. 



Richard Owen, Esq., in the Chair. 



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

 of the Dipodida, including the Jerboas and Gerbillas*. 



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

 then read some Notės 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 -vvhile the usual length of the largest malė 

 Cachalots, taken in the South Seas, is about 60 feet, that of fuU- 

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



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

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

 The upper jaw usually deseribed 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 generaUy corresponding 

 to the intervals bet\veen them. The entire length of these teeth is 

 about three inches ; 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 nuraber is not readily ascertained, because the whole Neries 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 betvi^een the pectoral fin and angle of the lower jaw. Its 

 situation is chiefly marked by a raised portion of integument around 

 •it. The aperture for vision does not exceed 2 inches in the longitu- 

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

 cilia and taršai cartilages ; they are composed of two horizontai bands 

 of integument, each, in the example from which I describe {v\z. a half- 

 grown malė), tvro 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 soraewhat 

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

 surface or hinge on which the lids movė. 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 \vith a dense layer 



• The abstract of this and the conchiding; part of the Memoir will be 

 found in the Proceedings for December 27, 18.S6. 



No. XLVIII. — Proceedings of thk Zoolouical Suciety. 



