BEAKED WHALES, FAMILY ZIPHIID^ TRUE. 13 



notches (straight) is 312 mm., while in the hirgest adult among the European speci- 

 mens this distance is only 260 mm., and in the thoroughly adult Nantucket specimen 

 282 mm. 



SKULL. 



The Atlantic City and Long Branch skulls also agree in numerous other details 

 of structure in addition to the foregomg, the more important of which will now be 

 mentioned. Unless otherwise stated, the ty]:)e-skull, as shown by Van Beneden and 

 Gervais' figures, ° also presents the same peculiarities in contrast with M. hidens. 



Dorsal aspect (PL 2, figs. 1 and 2). — The premaxillse are more depressed imme- 

 diately in front of the blowhole than in M. hidens, which, with the prominence of 

 the maxillary ridges, makes this whole region appear strongly concave. The blow- 

 hole is narrower absolutely and also relatively to the breadth of the expanded 

 proximal ends of the premaxillse, so that while in hidens the breadth of the blowhole 

 is much more than one-third the breadth across the proxmial ends of the premaxillse, 

 in europseus it is considerably less than a third. Both premaxillse are much con- 

 stricted on the sides of the blowhole and the effect is heightened by the greater 

 expansion of the proximal ends of the former. These ends do not fit closely against 

 the adjoming edge of tlie maxillaj as in hidens, but leave a transverse vacuity, or 

 trough, which is especially noticeable in the t}^)e-skull. The anterior end of the 

 malar bone occupies the bottom of the maxillary notch and a small portion of it is 

 visible from above, while in hidens it does not extend up into the notch at all from 

 the infei'ior surface and is not visible from above. The posterior margin of the 

 maxillfe is more squared in europxus than in hidens. 



The margins of the beak, formed by the maxillee, instead of being straight, are 

 somewhat emarginate a little posterior to the middle of the length and somewhat 

 convex anterior to it, which gives the contour of the beak, seen from above, a 

 different shape from that of hidens. In the t\'pe-skull of europseus the mesirostral 

 ossification appears to be higher at the proximal end than the premaxillse, and 

 distally extends to the end of the beak. In hidens it is lower than the premaxillse 

 and, in the Xantucket skull at least, ends anteriorly at the same point as the vomer, 

 or, in other words, much behind the end of the beak. It would appear from the 

 statements of Sir William Turner, "\'an Beneden and Gervais, Grieg, and others, 

 that the mesirostral ossification never reaches the end of the beak in hidens, but it 

 does in grayi, Tiaasti, densirostris, and many fossil species, as well as in europseus. 



Lateral aspect (PL 8, figs. 1, 2). — The temporal fossje are a Httle longer than 

 the orbit in europseus, but a httle shorter than the orbit in hidens; in the former the 

 superior margin is flat or a little concave, rather than convex. The exoccipital 

 extends in an angle farther forward in europseus, and the suture between it and the 

 zygomatic is, in consequence, less nearly vertical than in hidens. The premaxilliB 

 at the sides of the blowhole are nearly horizontal, so that their superior surface is 

 httle seen from tliis aspect, wliile in hidens they slope downward, so that the whole 

 of the superior surface is visible. The liigh maxillary ridge, situated beliind the 

 anteorbital notch, is very noticeable from this point of view, as it shuts off a 



OstiSographie, plate 24. 



