AND OTHER SPECIES OP CEPHALORHYNCHUS. 635 



well in front of the condyle. In C. heavisidei («) the coronoid 

 process is directed backwards, so that its apex lies but little in 

 advance of the condyle, while from its front end the upper edge 

 of the jaw slopes down to the teeth, instead of remaining at fii^st 

 horizontal, as in the other two species ; and the jaw is slighter 

 and has less vertical depth than in them. 



Pterygoid. — The importance of these bones in distinguishing 

 genera in the Delj>hinid£e was 23ointed out by Flower (1883), who 

 relied on Van Beneden and Gervais' figure (pi. xxxvi. fig. la) 

 for evidence as to CephcdorhyncIntSj and repi'oduced it on p. 473. 

 There can be no reasonable dovibt that the figure was drawn from 

 a skull with incomplete pterygoids, and it is thus to some extent 

 misleading. The type-skull of C. heavisidei resembles the figure 

 as reproduced by Flower, in respect of the pterygoids, but a, 

 comparison with the two skulls of C. commersonii, in both of 

 which these bones are complete, shows that they are much 

 longer than would be inferred from that figure. They resemble 

 in shape the pterygoids shown by Flower (1883, p. 471) in Glohi- 

 cephcda (Globiceps), but their posterior margin is more oblique, or 

 less nearly transverse. In skull A (PI. III. fig, 1), the palatal 

 surface of each pterygoid measures 36 mm., from the point where 

 it leaves the vomer, to its posterior tip. In their free, posterior 

 portions the two bones are separated by a narrow, O-shaped 

 interval, 18 mm. long and widening to 8 m.m. across, at the com- 

 mencement of the posterior oblique borders. Skull B is similar, 

 except that the interval between the free parts of the pterygoids 

 is A-shaped, and the length to the tip is only 30 mm. The 

 pterygoids are incomplete in Moreno's figure. 



99 29 



Teeth. — Skull A {C. commersonii) has " _^ teeth visible with^ 



out cutting away any of the gum. One or two small ones may 

 perhaps be present, beneath the gum, at the anterior end of the 

 series. In skull B, in which many of the teeth are wanting, 

 the number is about 29 on each side of each jaw. In C. heavisidei 



27 27 



(type), the number is ^ ^^ , while in C. eutropia (tyj)e) it is 



30-31 on each side of each jaw. 



The osteological features of the Cetacea are so variable that it 

 is often impossible to be sure how far characters selected from an 

 examination of a limited amount of material are of any value. 

 It is thus important to point out that, in the features enumerated 

 above, the two skulls of C. commersonii are in substantial agree- 

 ment with one another, except where attention is called to a 

 difference. There is evidence, moreover, that other specimens 

 of C. heavisidei agree with the type-skull. The skull of this 

 species has been figured and briefly described by Schlegel (1841, 

 p. 31, pi. iii. figs. 1, 4; pi. iv. fig. 6); and by Yan Beneden and 

 Gervais (1868-1879, p. 599, pi. xxxvi. figs. 1-1 b), from a skull in 

 the Paris Museum. The latter authors were inclined to regard 

 the specimens of Cejjhaloi'hyiichush'om. y-Avious south eiii localities 



