3G 



BRITISH FOSSIL CETACEA 



answering to those marked d, in tlie illustrations of this Monograph {Ziphius Lai/arcJi, 

 PI. I, fig. 2, d, ct passim), opening or commencing, as usual in ZiphuH, at the fore end or 

 apex of an infundibular cavity. The right premaxillary is unsynnnetrically expanded in 

 the narial region. The maxillaries are too much mutilated to show the position of the 

 antorbital foramina {h, b, in the figures of the present Monograph), but the outer margin 

 of the maxillaries is grooved, as usual, by " un sillon tres-marque," answering to e, g, of 

 the same figures. 



The vomer puts in a carinate appearance on the palate, nearer the palatine bones than 

 in ZipJiius Layardi ; but this is a difference of barely specific value when unassociated with 

 better characters. The constituent bones of the fossil fragment of rostrum described and 

 figured by Prof. Van Beneden (op. cit.) appear to have been in some degree separated 

 from each other, indicative, like the separate state of the atlas, of the nonage of the indi- 

 vidual. How far the non-ossification of the prefrontal cartilage may bear the same inter- 

 pretation may be questioned. 



The rostrum is restored (pi. i, fig. 1, vol. cit.) by continuing forward the lateral 

 contours of the maxillary parts of the preserved base of the snout with the same degree 

 of convergence to the problematical end, which, of course, makes the snout abnormally 

 short for a Ziphioid. One sees, however, how deceptive such basis of restoration may be, 

 by continuing, in like manner, the lateral contours of the expanded parts of the maxilla- 

 ries forming the base of the prolonged rostrum in most of the Zlphii figvned in the present 

 Monograph. 



This at least may be safely affirmed, that it is somewhat premature to propose a new 

 genus of Cetacean on the fragmentary and decomposed fossil representing the Placo- 

 zip/iius Duhoisii of Van Beneden. 



ZiPHiopsis, Du Bus. — The first character assigned to this genus ^ raises the question 

 whether ' proportionate length of rostrum' be available for generic distinction. The inade- 

 quacy, to that end, of ' direction of rostrum,' in view of the slight deviations from straight- 

 ncss hitherto observed in recent and fossil Ziphioids, has already been mooted. I note, 

 also, that examples cited of the genus Ziphiopsis do not give the length of the rostrum. 

 Z. phymatodes, e. g., is represented by a fossil rostrum with the end broken off'.^ 

 If the end of the rostrum of Ziphius Layardi, e. g. (PI. I, fig. 3), were broken off 

 anterior to the vomer (13), it might seem to have had one of but moderate length. 



1 " Rostre de moj'enne longueur, droit, a peu pr^s aussi liant que large. Ma.xillaircs superieurs tres- 

 epais. Canal vomerien petit. Incisifs nicdiocrement developpes, a. bords internes soudes ensemble dans 

 toute leur partic rostrale, depuis la fosse prenasale jusqu'a la pointe." — ' Bulletin de I'Academie Royale des 

 Sciences, &c., de Belgique,' torn, xxv, p. 628. 



* " Le vomer apparait a la surface palatine, vers le milieu de la longueur du museau, et disparait vers 

 son extremite', entre les orifices auterieures des canaux palatins. Un peu au dela la pii-ce est brisee." — 

 p. 628. A second specimen is only un peu plus complet." — lb. My experience warns against inferring 

 the length of the rostrum in a Ziphius in a specimen not havibg that part entire. 



