Prof. Eschricht on the Gangetic Dolphin. 175 



in the whalebone-whales). Another and more substantial objec- 

 tion to my explanation of the bony structure of the Gangetic 

 dolphin may, perhaps, be founded on this, that according to it, 

 the palatal bones can hardly be pointed out. But, convinced on 

 the one hand of the correctness of my account of the pterygoid 

 bones, and on the other, of the necessity of the existence of the 

 palatal bones, I have thought from the commencement, that they 

 must be those parts of the palate which are marked jo in PI. VII. 

 fig. I ; and I very soon satisfied myself, that they could not be the 

 foremost elongated bones of the palate, which I have noticed 

 above as plates belonging to the upper jaw-bones. It remains, 

 therefore, only to account for the little three-cornered, very thin 

 bony plate (also marked p) which appears on each side of the 

 median line of the palate, between the upper maxillary and the 

 pterygoid bone, as in the Hyperoodon. It is highly probable, 

 that the plate forms only a small part of some bone, which con- 

 ceals itself for the greatest part by the pterygoid bone ; and I 

 think even to have been able to discern, deep in the interior of 

 the nose, that it forms the lateral sides of the nasal cavities, be- 

 fore the pterygoid bones. The real state of the case can only be 

 decided by bursting a skull open. 



Cuvier points out, that the crests between the basilar and late- 

 ral parts of the occipital bone ('' cretes du basilaire et des occi- 

 pitaux lateraux ") which inwardly confine the vault under which 

 the ear is situated, are very thick and covered with minute bony 

 spiculse. The bulla tympani, he says, is very large and grown 

 together with the petrous portion, which latter is not simply 

 suspended (by means of fibrous tissue), but firmly wedged in 

 between the temporal bone and the surrounding parts of the 

 occipital bone. 



This condition of the petrous portion, as pointed out by Cuvier, 

 deserves some closer examination. In a preceding memoir (the 

 sixth on Cetacea*) I have pointed out, that while that portion in 

 the toothed whales, generally, is so loosely connected with the 

 skull, that it commonly drops off during maceration ; yet in some 

 of the species, and in all whalebone whales, it sends forth a pe- 

 culiar elongation, which enters between the temporal and occi- 

 pital bones, and reaches in some even as far as the outer surface 

 of the skull ; its labyrinth being at the same time embraced, as 

 it were, by protruding bony points of the temporal bone — by a 

 single small bony hook in the Cachalot, according to the dis- 

 covery of Peter Camper f. A similar structui-e exists in the 



* Transactions of the Royal Danish Academy of Sciences, Fifth Series, 

 Division of Nat. Hist, and Mathem., vol. i. Copenh. 1849, p. 94. 



t Observations anatomiques sur la structure interieure et le squelette 

 de plusieurs especes de Cetaces, publie par son fils Adrien-Gilles Camper, 



