6 



BRITISH FOSSIL CETACEA 



nasal fossae (22, 22') anteriorly, and partially reappear at fig- 2. The premaxil- 

 laries expanding at the sides of the nostrils developc each a ridge, extending toward 

 the nasals and dividing the prenasal fossae from the maxillary ones (21', 21')- 



The specimen figured (' Oss. Foss.,' loc. cit., pi. xxvii, figs. 4, 5, 6; fig. 5 being copied 

 in my figure 2) shows a rostrum of similar proportions to that in the type-species (fig. 1, 

 and ' Oss. Foss.,' loc. cit., fig. 3) ; but the prenasal fossae are more shallow, the premaxil- 

 lary walls being less elevated ; and a more marked difference is seen in the continued 

 ossification from the 'septum narium' or ' lamina perpendicularis' forward (fig. 2, 14'), 

 expanding to form a broad and dense mid-tract along the' upper surface of the rostrum 

 (as at / in Cuvier's figures 4 and 5, " crete plate, qui me paroit appartenir au vomer 

 par sa partie inferieure et elargie," ib., p. 354). I shall subsequently show that this mid- 

 tract does in the present and some other species of Zip/iius coalesce by its lower 

 expanding surface with the canaliculate vomer, and in that respect, but in that only, may 

 be said to belong thereto. 



The third specimen, also fossil (fig. 3), and from the same Mid-tertiary formation and 

 locality, resembles the second in the proportions of the rostrum, and in the continuous 

 ossification (uO of the cartilage extending forward from the 'septum narium' (14), and 



expanding as shown at / in Cuvier's pi. xxvii, fig. 7. 

 Only, whereas in fig. 2 ('Oss. Foss./ ib., fig. 5) 

 the prenasal fossae terminate anteriorly, each in 

 a foramen leading to a canal which reappears 

 further forward on the surface of the snout ; in fig. 

 3 (' Oss. Foss.,' ib., fig. 7) the fossae are continued by 

 open canals {d, d) to the same part of the snout, 

 gradually contracting forward to such canals. More- 

 over, in the present species, which may be noted as 

 Zipldus Cuvieri, the upper surface of the maxillaries, 

 from the anterior third of the rostrum to the sides of 

 the prenasal fossae {d, d), is roughened by irregular tu- 

 bercles and ridges. Thischaracter appears in diflferent 

 degrees in other fossil ZijjJdi, e. g. Z.gihhis, t. ii, fig. 

 2, e ; Z. [Ziphiopsis, Du ^\\?,.)pJii/mu(odes, &c. 



From the expanded superorbital platform of 

 the maxillaries (c, c, figs. 2 and 3), these bones 

 rapidly contract, with a concave outline to the base 

 of the rostrum, along the sides of which a ridge (<?) 

 Ziphius Cuvieri, Ow. ; z. pianirosiris, No. 2, Guv. continued for somo Way, gradually subsiding. 



The third species Ziphius, Cuv., is represented by a petrified edentulous rostrum ('Oss, 

 Foss.,' loc. cit., pi. xxvii, figs. 9, 10), with so much of the base as shows it to be of similar 

 composition with that in the preceding Ziphii, but in shape hunger and more slender. As 



