172 Prof. Eschricht on the Gangetic Dolphin, 



viewed with the base upwards) into an obhque wall, which slides 

 backwards over a plate of the temporal bone (PL VII. fig. 1 t) 

 lying before the bulla tympani (g^) ; but which in other respects, 

 and for the most part, occupies the temporal fossa, in as far 

 as its wall is formed of the frontal bone (/). 



Proceeding to the examination of the separate bones of the 

 palate thus constructed, we find (PI. VII. fig. 1) on the under 

 surface of the cranium, between the side-branches of the lower 

 jaw [x)j as we pass backwards, first, the hindermost part of the 

 palatal surface of the upper jaw with its four last teeth. From 

 thence ascends on each side, and in a parallel direction to the 

 branch of the lower jaw, the cleft, mentioned above as separating 

 the two plates of the upper jaw. Then follows the palatal surface 

 of the hindmost of those plates, reaching (where it is marked p) 

 up under the zygomatic bone, and above the temporal plate of 

 the frontal bone, with which it forms a large oblong hole, serving, 

 no doubt, for the passage of the palatal nerve of the fifth pair. 

 This surface is proportionally narrow, and runs parallel to the 

 cleft in the anterior margin of the upper jaw, and consequently 

 also to the lateral branch of the under jaw. The remainder of 

 this long palate — narrow if viewed along its high ridge only, but 

 of considerable breadth if viewed in conjunction with its two 

 oblique surfaces — is made up on each side of one single bone (w), 

 which in the dry cranium is perfectly hollow, consisting of two, or 

 more correctly three, thin, distant plates. One of these plates 

 forms the oblique surface just mentioned; the other forms the 

 hinder part of the side and floor of the nasal cavity (visible in 

 PI. VI. fig. 3 u) ; and the third, extending along the median line, 

 corresponds to the opposite plate on the other side, and joins 

 therefore the palatal plate, in the ridge itself of the palate, 

 where, in the macerated cranium, the entrance to the cavity 

 within is wide open. But here, as in the vaults of the upper 

 jaw, the cause of this last appearance lies in the destruction of 

 the periosteum and the bony network which it held together. 

 The proper entrance to the cavity is, where the palatal and 

 nasal plates meet, consequently along the posterior margin of 

 the bone, which looks directly towards the bulla tympani (PI. VII. 

 fig. I^). The inner surface in the median line seems to press 

 closely against that of the opposite plate. By carefully separating 

 the two (which was only practicable, to a sufiicient degree, in the 

 smaller cranium belonging to the Royal Museum), a second pair of 

 vertical plates was actually seen between them, inclosing another, 

 third pair, very delicate, like thin paper. Of these two concealed 

 pairs, the first is manifestly an elongation of the anterior part 

 of the palate, which has been mentioned as belonging to the 

 palatal plate of the upper jaw, but is marked p on the figure ; the 



