PEOFESSOR FLOWER ON THE RECENT ZIPHIOID WHALES. 219 



the ordinary mastoid in being united to the tympanic instead of the periotic. To the 

 anterior and inner side the tympano-periotic is supported by a long slender process of 

 the squamosal, with which it comes into closer contact than in the true Dolphins'. 



The tympano-periotic bones are slightly larger than those of Ilyperoodon (PI. XXIX. 

 fig. 6), but have much the same general form, with certain differences in detail, of which 

 the most important are : — in the tympanic the anterior (Eustachian) end (e) is more 

 prolonged, pointed, and spout-like ; the groove between the posterior lobes is deeper ; 

 the posterior articular surface (ff) for the periotic is larger and smoother ; the periotic 

 is more elongated, the notch between its anterior [a.l) and middle lobe {m.l) is wider, the 

 anterior lobe is more prolonged and pointed in front, and the orifice of the meatus 

 auditorius internus {i.a.in) is rather smaller. 



It is important to note that in every one of these points of difference, Hyperoodon 

 approaches nearer than Berardius to Physeter — a confirmation of the great taxonomic 

 value of the characters of this region of the skull. 



On comparing the median section of the skull (PI. XXVIII. fig. 7) with that of 

 Hyperoodon, the main difference is the smaller degree of elevation and of antero- 

 posterior compression in the great supracranial crest, and the greater extent, both in 

 vertical and antero-posterior direction, of the bony mass formed by the coalescence of 

 the presphenoid, mesethmoid, and frontals which lies in front of the cerebral cavity, 

 separating it from the nasal passages. In these, as in so many other respects, 

 Hyperoodon approaches much nearer to the Cachalot than does Berardius. 



The hinder edge of the vomer, which is prolonged beneath the presphenoid and basi- 

 sphenoid, is much less massive in Berardius than in Hyperoodon ; but, generally speaking, 

 the conformation of the cranium and the relations of the bones to each other as seen in 

 this view are strikingly similar^. 



The basioccipital and the basisphenoid have completely coalesced; but the fissure 

 between the latter and the presphenoid is open to the extent of more than a quarter of 

 an inch. The floor of the cranial cavity is less curved fi-om before backwards than in 

 Hyperoodon, and therefore much less than in Physeter ; and the commencement of the 

 spinal canal is not directed upwards to the same extent. The pitilitary fossa is very 

 indistinct ; but at some distance behind it there is a broad and deep groove on the upper 

 surface of the basioccipital. 



The cerebral cavity presents much the same general form and size as in Hyperoodon 

 and the allied species, being high, very broad, and flattened from before backwards. 

 Its greatest breadth is 11^ inches, its greatest vertical height 7 inches, its length 

 8 inches. The posterior upper part has a strong median projection, or osseous falx 



' See the description of this region in Hyperoodon by Eschricht (op. at. p. 45), and in Ziphius indicus by 

 Van Beneden. 



^ The comparison was made with the skull of a Hyperoodon of corresponding age in the Museum of the 

 College of Surgeons ; it is figured in Trans. Zool. Soc. vol. vi. pi. 56. fig. 3. 



VOL. VIII. — PAKT III. September, 1872. 2 k 



