218 PROFESSOR FLOWER ON THE RECENT ZIPHIOID WHALES. 
distinct irregular and freely moveable wedge-shaped pieces of bone of the nature of the 
so-called “* Wormian bones.” 
The mesethmoid (ZZ) forms a strong ridge between the narrow nostrils, rising to a 
level with the premaxille; its ossification becomes irregular and nodular anteriorly, 
and extends as far forwards as 2 inches in front of the base of the rostrum (7. e. a line 
drawn between the deepest part of the two anteorbital notches, and which is supposed 
to mark off the rostrum from the cranium proper). In the Paris specimen the ossifica- 
tion extends somewhat further, doubtless in consequence of the superior age of the 
individual; but it is not likely that it ever attains to the remarkable extent and 
solidity characteristic of some species of Ziphiinee. 
As in Hyperoodon and other allied forms (but not in Physeter) the bone which lies 
in ordinary Dolphins beneath the anterior part of the orbital plate of the frontal, in 
contact with the maxilla in front, the frontal behind, and the palatine on the inner 
side, is divided by a distinct suture into two parts. ‘The anterior part gives origin to 
the slender zygomatic arch, and undoubtedly corresponds to the malar of ordinary 
mammals; while the posterior part appears to represent the lachrymal, as pointed out 
by F. Cuvier’, Eschricht?, Van Beneden’*, and others, though Duvernoy considered it a 
prolongation of the orbito-sphenoid. 
There are several differences in detail in the form and arrangement of these bones 
between Berardius and Hyperoodon, one of the most important being that the orbit of 
the former is considerably smaller than that of the latter, which, together with the 
inferior size of the optic foramen, would indicate a smaller organ of vision. 
The zygoma, like that of Hyperoodon, is broader and flatter, especially at its anterior 
extremity, than in the ordinary Dolphins. . 
A most important and characteristic region of the base of the skull in the 
Cetacea, as in other Mammals, is that surrounding the organ of hearing. Here 
Berardius agrees with the other Ziphioids in showing affinity to Physeter‘ rather 
than to the true Dolphins, both in the form of the tympanic bulla, and in the greater 
fixedness by which it is attached to the skull. This is chiefly effected by a large 
irregular wedge-shaped process (Pl. X XIX. figs. 1 & 2, m), which passes backwards and 
outwards from the hinder edge of the portion of the tympanic which articulates with 
the periotic, and lodges in a groove between the exoccipital and squamosal, reaching 
the external border of the skull. This process so closely occupies the position of the 
“mastoid” in ordinary Mammals, that it has very naturally received that name: but its 
exact homology must be cleared up by a study of its development; for it differs from 
* Histoire Naturelle des Cétacés (1836), p. 76, pl. 7, 1, 
* Untersuchungen iiber die nordischen Wallthiere (1849) p. 44. 
* Mém. sur une nouvelle espéce de Ziphius, Mém. de YAcad. Royale de Belgique, coll. in-8yo, tome xvi, 
1863, p. 14. 
+ And more remotely to the Whalebone Whales, as pointed out by Eschricht, 
