Prof. Eschricht on the Gangetic Dolphin. 171 



between their two plates ; and that they are seen open only in 

 the macerated cranium, because the inner plate is partly mem- 

 branous and invested in a net of delicate bony spiculse, which 

 is destroyed during the process of putrefaction, together with 

 the membrane itself. Guvier states quite correctly, that the 

 cavity covered by this bony vault is filled in the fresh indivi- 

 dual with a dense and somewhat hard mass of fibres; but it 

 must not be supposed, that this mass penetrates the cavities 

 or cells of the bone itself, it being in contact only with the 

 periosteum of the bony sides. The wide gap between the two 

 plates of these crests appears already on their anterior margin, 

 and on that of the whole upper jaw (PI. VII. fig. 1, behind and 

 parallel to the branches of the under jaw). 



Cuvier continues : " Les fosses temporales de cette espece sont 

 beaucoup plus grandes que dans aucun dauphin, en sorte que leur 

 cretes superieures cernent k la partie superieure de Pocciput* un 

 espace rectangulairef de deux cotes duquel part a angle droit le 

 reste de la crete occipitale. La suture de Pocciput avec les tempo- 

 rauxj et avec les parietaux§ suit precisement cette crete angu- 

 leuse ou occipito-temporale. L'occipital s'avance dans Pespace 

 rectangulaire que nous venons de dire, pour s'articuler en avant 

 avec le frontal ||. Une autre particularite de cette tete, c^est la 

 grandeur de son apophyse zygomatique du temporal^ qui est 

 proportionnee k la grandeur de la tempe. EUe va aussi se joindre 

 a Papophyse postorbitaire du frontal ** et forme ainsi k elle seule 

 toute Papophyse zygomatique." 



It must be observed here, that this remark applies, on the whole, 

 to all Cetacea, where the zygomatic bone, however long it may 

 be, especially in dolphins generally, always forms the lowest 

 margin of circumference of the orbit, but never of the temporal 

 fossae; exactly as is seen in the Gangetic dolphin. In dolphins 

 the process of the zygomatic bone is applied, backwards, to the 

 inner surface of the zygomatic process of the temporal bone; 

 and this, too, is decidedly the case in our species (PI. VII. fig. 1 z), 



"L'orbite etant tres-petit, la tige de Pos jugalff qui le borne en 

 dessous est beaucoup plus courte que dans les autres dauphins ; 

 elle est large et comprimee. Le corps de Pos J J est plus renfle 

 que dans les autres, mais est place de meme sous les parties 

 voisins du frontal et du maxillaire§§" (p. 299). 



The real difficulty in explaining the bones of the cranium 

 of the Gangetic dolphin exhibits itself only as regards the 

 palate. This has the form of a small, prominent ridge along 

 the median line, descending on both sides (if the head is 



* Tab. 1. fig. 2. t Tab. 2. fig. 1 o (the middle). t Ibid. fig. h. 

 § Ibid. ^ II Ibid./. % Ibid. ^'. ** Tab. 1. fig. 2. 



tt Tab. 3. fig. 1 z. XX Ibid. fig. 2z. §§ Ibid. fig. 1, 2. 



