218 PEOFESSOR ELOWER 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 (ME) forms a strong ridge between the narrow nostrils, rising to a 

 level with the prsemaxillse ; its ossification becomes irregular and nodular anteriorly, 

 and extends as far forwards as 2 inches in front of the base of the rostrum (i. 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 Ziphiinse. 



As in Eyperoodon 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 1 , Eschricht 2 , Van Beneden 3 , 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 Uyperoodon, 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 4 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 (PI. XXIX. figs. 1 & 2, to), 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 



1 Histoire Naturelle des Cetaces (1836), p. 76, pi. 7, 1. 



2 TTntersuclmngen iiber die nordischen Wallthiere (1849) p. 44. 



3 Mem, sur une nouvelle espece de ZipMus, Mem, de l'Aoad. Royale de Belgique, coll, in-8vo, tome xvi. 

 1863, p. 14. 



4 And more remotely to the Whalebone Whales, as pointed out by Eschricht. 



