Prof. Eschricht on the Gangetic Dolphin. 169 



tion the line of separation is no longer discernible (PI. VI. fig. 2). 

 It is further stated by Cuvier, that the intermaxillary bones ascend 

 to the sides of (PI. VI. fig. \i,i,i), and even above {ibid. ++) 

 the nostril, which in this species is longer than broad. It may 

 not be improper to add to this notice of the external nostril some 

 remarks on the connexion of the bones of the aperture in the 

 Dolphins generally, and in the species before us particularly. 



The extension of the intermaxillary bone to the sides of the 

 nostril, as far as the outer and even upper margin of the nasal 

 bones («, n), holds good also in most other Cetacea ; that is, all 

 whalebone-whales, and among the toothed, at least the long- 

 jawed whales, or dolphins proper, as also the Hyperoodon; whereas 

 they do not reach so far back in most of the short-jawed whales, 

 for instance in Delphinus globiceps, and especially the porpoise. 

 The same difference occurs also, as is well known, among other 

 mammalia, where the intermaxillary bones generally reach to 

 the lateral margins of the nasal bones, which however is not 

 the case, for instance, among Ruminantia. It is assumed, com- 

 monly, that in all cases those bones form the anterior (in 

 the human skull the lowermost) margin of the outer nostrils. 

 But, strictly speaking, this is not exactly the case with the 

 Gangetic dolphin, nor with other cetacea, or mammalia gene- 

 rally; at least never from the commencement. The aperture 

 is originally covered behind by a cartilaginous wing, which is 

 placed transversely (cleft into two side-wings in whalebone- 

 whales and most other mammalia*), and proceeds from that 

 part of the primordial cartilaginous cranium, which subsequently 

 becomes the ethmoid bone; and before, on each side, by a 

 cartilaginous wing, originating from the lateral surface of the 

 part of the said primordial cranium which forms the partition in 

 the cavity of the nose, and is afterwards more or less embraced by 

 the vomer from below. The posterior cartilaginous wing (or the 

 posterior pair) disappears perhaps in all mammalia, except in 

 some whalebone-whales, where it seems to continue cartilaginous ; 

 at least in many toothed whales (among these the porpoise), 

 it becomes osseous and covers the lower third of the nasal 

 bones, as a distinct bony plate, between the free portion of the 

 nasal and ethmoid bones. I could not discover this bony plate 

 in the Gangetic dolphin ; but I found a depression on the lower 

 part of the bones of the nose for the cartilaginous wing, which 

 most probably had been lost during the process of maceration. 

 Among most mammalia the anterior pair of wings likewise disap- 

 pears ; but it becomes ossified in others, such as the hog, and 



* See my fifth memoir on Cetacea, in the Transactions of the Royal 

 Danish Academy of Sciences, div. Nat. Hist, and Mathem., vol. xii. Copenh. 

 1846,1 13. f. \,e. 



