PSEUDORCA CRASSIDENS. 201 



great broad-nosed dolphins having only a feeble, or defective set of teeth, whereas the form of 

 the lower jaw of our crassidens and the killers is called forth and necessitated by powerful 

 and large teeth. It is further a consequence of the size of the teeth, that the dental row, just as 

 in the killers, occupies the larger half of the whole length of the jaw, although the teeth are 

 hardly so numerous as in the ca'ing-whale, in which the dental row (even before a single tooth 

 has as yet fallen out) does not occupy more than a third of the jaw ; and finally, and partly for 

 the same reason, the difference between the greatest height of the jaw behind and its smallest 

 height close to the symphysis, is not so considerable as in the ca'ing-whale, and the symphysis 

 itself is comparatively longer than in the latter species ; but in these two respects also 

 our dolphin bears a close resemblance to the killer. The considerable size of the teeth (com- 

 paratively speaking, scarcely smaller than those of the killers) has already been briefly alluded 

 to, we must now give a more minute description of them. They are slightly curved in an 

 inward direction, and placed in deep sockets, which both in the upper and in the lower jaw are 

 completely separated from each other through their whole extent, whereas the sockets of the 

 teeth of the killers are most frequently only imperfectly separated. Only between the two 

 hindmost sockets the partition may sometimes disappear, and the cavities may thus become 

 more or less completely coalesced. In the lower jaw, the foremost socket approaches the point of 

 the jaw as much as possible ; but such is not the case in the upper jaw, as the inter maxillaries 

 project in front of it, though only very slightly. The roots of the teeth seem to close 

 much faster than in the majority of the killers ; at least the roots are still perfectly open in 

 the teeth of several crania of a species of large killer from the seas round the Faroe Islands, 

 which belonged to animals middle-aged, at least, rather than to young ones; whereas the 

 teeth even of the Refsnæs individual of the species here described have their roots perfectly 

 pointed, and it is only in the largest teeth that an insignificant aperture is left in the points of 

 the roots leading into rather a narrow internal cavity. In the upper jaw, the teeth increase in 

 size progressively backwards up to the last tooth, which becomes suddenly again con- 

 siderably smaller than the preceding one ; in the lower jaw, the foremost tooth is also very small, 

 scarcely half as large as the second one; then the teeth uniformly increase in size up to the 

 seventh or eighth, which are of about the same size ; the ninth is again a little smaller, and the 

 hindmost again less than half the size of this one. The teeth are almost of the same size in 

 both jaws ; the largest are two and a half inches in circumference just above the alveoli, and 

 have a length of about three inches, of which the enamelled crown occupies about one third. 

 The number of the teeth is subject to individual differences ; Mobius^ states that the number of 

 the teeth of the individual caught in the harbour of Kiel, is twenty in either jaw, ten on 

 either side, and Professor Behn has confirmed this statement in a letter to the author of this 

 memoir. But this number we do not find repeated in any of the individuals stranded on the 

 Danish coasts, nor do the latter quite agree with one another as to the number of their teeth. 

 Thus, the individual stranded at Middelfart has nine teeth on either side of either jaw, the 

 total number being smaller by four than in the Kiel dolphin, and there is not the slightest trace 

 of its having had more teeth at an earlier period of its life. In the Asnæs specimen, the teeth 

 had fallen out, and only one or two were found lying on the beach, where the body was landed ; 

 but by the quite uninjured sockets we may ascertain with perfect certainty, that this individual, 



^ 1. c. page 3. 



26 



