CETOTOLITES. 527 



An entire specimen of this compound bone has not yet 

 been obtained from the Red-crag ; nor is it likely that it 

 should be. Almost all the fossils of this formation show 

 the action of surf- waves or breakers ; those under con- 

 sideration appear to have been dislodged from a subjacent 

 eocene deposit ; and as the massive petrous bone and the 

 tympanic bone of the Cetacea adhere to each other natu- 

 rally by only two small surfaces, they would hardly escape 

 being broken asunder under the operation of such disturbing 

 forces. 



All the specimens which were submitted to me by Pro- 

 fessor Henslow consisted of the tympanic portion only, 

 and I have as yet seen but one specimen of the rugged 

 petrous bone ; it is now in the collection of Mr. Brown, of 

 Stanway. The tympanic bone may be readily recognised 

 by its peculiar conchoidal shape and extremely dense tex- 

 ture ; the recent bone breaking with almost as sharp a 

 fracture as the petrified fossils. 



None of these tympanic fossils are entire : the thin 

 brittle outer plate which bends over the thick, rounded, 

 and, as it were, involuted part, like the outer lip of such 

 simple univalves as the Buttee and LeptoconcM, is broken or 

 worn away in the best specimens, all of which are rolled 

 and waterworn. I was at once led by their size to the 

 largest of the existing Cetacea for the subjects of com- 

 parison, as the Grampus, the Hyperoodon, the Cachalots 

 (Pkyseter), and the true Whales (Baleenoptera and Baleena). 



Two or three of the specimens were fortunately sufficiently 

 entire to show the form of the tympanic cavity bounded by 

 the overarching plate, with the proportion and direction of 

 its anterior or Eustachian outlet, and most of them had the 

 opposite or hinder extremity entire. They were thereby 

 seen to differ from the tympanic bones of the Delphinid<z, 



