36 Frederick Glaqmidu: 



Ohseri'dlions. — Meso2)h)do/i agrees with the other beaked whale^ 

 Ziphius (of which there is probably only one living species), in hav- 

 ing an ossified niesethmoid, but the nasals joined together form the 

 vertex of the skull in the latter genus. In Hyperoodon, the bottle- 

 nosed whale, there are large longitudinal ci-ests on the maxillae at 

 the base of the rostrum. In Berardiiis the mesethmoid is only par- 

 tially ossified. Chonezijyhius has the mesethmoid cartilage non- 

 ossified, and there is a fistular cavity throughout the short, thick 

 rostrum. According to Flower, the tympanic bone of Berardiiis is 

 exactly like that of Mesoplodon.'^ 



The chief character given by Owen for the cranial rostrum in the 

 species comjtressiis is " the predominance of the dimensions of depth 

 over that of breadth at every part of the extent of the specimen 

 figured." Prof. Owen also states that " the pre-frontal mid-tract 

 is transversely convex from its beginning, the convexity increasing 

 as it advances; and, from the low position of the ecto-maxillary 

 ridges and the steep slope thereto of the premaxillaries, the mid- 

 tract seems, of itself, to constitute the upper surface of the rostrum," 

 In Huxley's specimen the same character of great vertical depth pre- 

 vails, with the exception of the extreme posterior, where it is wider 

 tlian deep. This exception would also most likely have obtained 

 in Owen's specimen, but for the fact that the posterior area adja- 

 cent to the narial openings is wanting. 



The only apparent differences between Huxley's and Owen's speci- 

 mens are that, in the former, the sectional outline is more distinctly 

 rhomboid, and there is a slit in the mesethmoid band '' about 2^ in. 

 in front of the upper apertui-es of the canals," . . . . " Avhich 

 deepens as it passes backward and becomes lost in an irregular 

 fossa." This median slit is not present in the nearly perfect Aus- 

 tralian specimen from Grange Bvirn, so that in this point it agrees 

 with Owen's example. On the other hand, another specimen from 

 Grange Burn, Avhich is in Mr. Dillwell's collection at Hamilton, and 

 of which there are casts in the National Museum, shows a distinct 

 median slit, as in the Huxley example, and much longer, measuring 

 4f in. The two Grange Burn specimens have been carefully 

 examined and measured, Avith a view to discovering any definitely 

 separable characters, but with the result that one feels bound to 

 conclude that the slight differences between them represent merely 

 individual variation, such as are evident in living species of this 

 genus. For example, the median slit probably representing a vesti- 



1 Flower. Uiid., vol. x., 1878, p. 423. 



