170 ESCHRICHT ON THE 



narrow, and seem to be but slender and feeble when compared with those of the killers. That 

 the former, as well as the latter, must be excellent swimmers is perfectly evident. Never- 

 theless, the killers seem, as to the ease and variety of their movements, to be inferior 

 especially to the dolphins properly so called, whose activity is well known to voyagers 

 who have seen them follow the fastest sailing vessels for miles, occasionally diving under 

 them, or swimming in a circle around them with an agility sufficiently expressed in the lightness 

 of their comparatively meager body, the slenderness of their limbs, and the great number of their 

 vei-tebræ ; but on the other hand these dolphins seem to be surpassed by the killers in the 

 power of their movements. Their pectoral fins may still be called rather long in proportion to 

 those of most of the other toothed-whales, but their special character is, properly speaking, in 

 their being at the same time almost as broad as long (the proportion is nearly as 5 : 6). 

 Such is also the case with their caudal fin, that is to say, its two lobes are not remarkable for 

 their length but for their powerful structure. Their vertebrae are only few in number ; fifty- 

 two, fifty-three, or at most fifty-four, but, like the ribs, they are, comparatively speaking, 

 extremely large and strong. 



It is, however, especially by the organs of mastication, or rather of prehension, that the 

 greater power of the killers is expressed, that is to say, by the jaws with the muscles by which 

 they are moved, and in the jaws themselves, by the teeth. It is in these organs of prehension, 

 and particularly in the teeth, that we must seek for the most essential character of this group 

 of rapacious whales in the stricter sense of the word, standing so isolated in the order of the 

 Cetaceans. 



In the Cetaceans, as well as in all other mammalia, the power by which the jaws are 

 pressed together, is indicated by the circumference and depth of the temporal fossæ. In the 

 killers these are comparatively larger and deeper than in any other Cetaceans. An Orca cranium 

 stands, in this respect, in almost the same relation to the cranium of many other cetaceous 

 animals, for instance, to that of a Beluga, or of a dolphin properly so called, as the cranium of 

 a lion to that of a horse or ruminating animal. The contrast appears, perhaps, least striking, 

 when the cranium of a ca'ing-whale is compared with that of a killer, but in the former the 

 muscular power operates under much greater disadvantages, the teeth being confined to the 

 foremost third of the jaws, whereas in the killers the whole length of the dental margin of the 

 jaws is furnished with teeth, the largest of which occupy the middle part. The upper jaw of the 

 ca'ing-whale has also almost the same breadth as that of the killer ; but this breadth is prin- 

 cipally owing to the inter maxillaries, evidently in order to give a broader substratum for the 

 adipose swelling on the head, as in the cachalots ; in the killers, on the contrary, the considerable 

 breadth of the upper jaw is principally produced by the superior maxillaries, and the breadth of 

 the latter is again necessitated by the very large teeth fixed into it. 



The teeth of the killers are, in several respects, distinguished from those of all other 

 Cetaceans. Their free portion resembles that of the cachalot's teeth, representing, as in 

 these, a curved cone with an obtuse point and a comparatively broad base, only that it is most 

 commonly somewhat compressed having two indistinct margins, an exterior one convex, and 

 an interior one concave ; but more minutely examined, especially when cut through transversely, 

 it is observed to have quite a different structure, for whereas the cachalot's teeth only consist of 

 dentine covered with cement, but without any enamel, at all events, except at the extreme tip, 

 from which it is soon worn dS, the teeth of the Orcas are on the contrary provided with 



