4 



BRITISH FOSSIL CETACEA 



greatly extend transversely the interorbital platform, of which they constitute the two large 

 lateral wings or concavities ; they are continued forward along the under part of the sides 

 of the rostrum, and for some distance in the form of an outstanding ridge (fig. 1, e,e). 

 The upper mid-tract of the rostrum (' vomer/ h, of Cuvier) is formed by a production of the 

 ' lamina perpendicularis aethmoidei,' answering to my prefrontal/ of singular thickness (fig. 

 1, u')- The lower mid-tract of the rostrum is, in part, formed by the veritable vomer. This 

 rostrum was edentulous. 



From the longitudinal extent of the prenasal fossa, through interruption of ossification 

 of the prefrontal, between i4 and i4', in fig. 1 {k and h of fig. 3, pi. xxvii, 'Oss. Foss.'), 

 Cuvier gave to this original type of his new genus the specific name Ziphius cavirostris. He 

 notes the cetacean character of want of symmetry in the twist of the nasal bones to the left ; 

 and that the contiguous plate of the right premaxillary is the largest, while, in the fossa (ib., 

 o), the left premaxillary is the largest ("dans la grande fosse c'est le gauche qui reprend de la 

 largeur et qui rejette vers la droite la suture qui la separe de I'autre" (tom. cit., p. 351). The 

 posterior wall of the nasal chamber is perforated on each side the septum by a aingle orifice ; 

 Cuvier writes — "pour la communication du nerf olfactif avec les cavites nasals -." it more pro- 

 bably transmitted, as in BeljMnidcB and Hyperoodon, the nasal branch of the first division 

 of the trigeminal nerve, with accompanying branches from the anterior meningeal artery. 



Cuvier adds that this skull was very heavy and very dense ("cette tete est tres pesante,tres 

 dure," ib., p. 352), by which he may be recording another character of his genus, viz. the 

 singular petrosal density of much of the osseous texture ; this character, however, he 

 believed to be due to posthumous petrifaction of the specimen, and so deemed it to 

 belong to a fossil Cetacean. The specimen, now in the Museum of Comparative Anatomy 

 at the Jardin des Plantes, though not " completement petrifiee en calcaire," ib., does 

 appear to have imbibed calcareous matter, probably by long imbedding in the superficial 

 deposit from which it had been dislodged. 



The new and more enlarged view of the expanded interorbital part of Cuvier's original 

 or type-specimen of ZipJdus cavirostris, which Prof. Gervais has given," is chiefly for the 

 purpose of comparing it with a similar view of the skull of a Ziphius found in 1850, on the 

 beach of Aresquiers, Departuient of Herault, which ZipJdus, still existing in the adjoining 

 seas, he refers to the same species — Z. cavirostris? In this instance the mandible was 

 obtained, showing one of the series of germs of teeth in the alveolar groove of each ramus to 

 have been developed at the end of the symphysis.* The small size of this protruding tooth 

 may relate to sex, and indicate the stranded Ziphius to have been a female. M. Gervais notes 

 that the prenasal fossa (his 'excavation conchoide') is deeper and less expanded (" moins 

 evasee et plus considerable," op. cit., p. 8) than in Cuvier's specimen, owing to differences in 

 the direction and development of the premaxillary walls of the fossa. But M. Gervais is 

 inclined to include these differences within the range of sexual or individual varieties of 



' 'On the Archetype and Homologies of the Vertebrate Skeleton,' 8vo, 18-18, p. .58. 



^ 'Zoologie et Paleontologie francaises,' 4to, pi. xxxviii, fig. 2 ; woodcut fig. 1 of present Monograph. 



3 Op. cit., p. 154, pi. xxxviii, fig. 8, and pi. xxxix, figs. 2 — 7. * Op. cit., pi. xx.xix, figs. 4, 4a. 



