18/6.] A YOUNG DELPHINUS ALBIROSTKIS. 085 



The characters of the skeleton are almost identical in both. Thus 

 the present specimen agrees with Z>. albirostris in the number of the 

 vertebrae and in the peculiarities of the cervical vertebrae. There are, 

 indeed, a few points of difference to be detected in the skull ; but 

 these are of minor importance and probably merely the differences of 

 youth and age. 



The differences of import are to be found (1) in the character of 

 the markings, (2) in the general shape of the body, (3) in the 

 position of the dorsal fin. I consider, however, that the extreme 

 youth of the specimen may account for the first two of these dissimi- 

 larities. The discrepancy in the markings is not great, and consists 

 chiefly in the white patches on the side being more strongly pro- 

 nounced and more distinctly separated by the black. Then as regards 

 the difference of shape, we know that a massive head, or a head large 

 in proportion to the rest of the body, is a peculiarity of youth in 

 many animals. The position of the dorsal fin in relation to the 

 middle vertical line, however, is a difficulty not so easily got over ; 

 we can scarcely suppose that as the Dolphin advances in age, the 

 dorsal fin advances upon the back, at least to such an extent as to 

 lie entirely in front of the middle vertical line. But the drawing of 

 Van Beneden is the only guarantee that we have of its position in 

 front of this vertical line ; and as we have already seen this to be in 

 fault in one or two particulars, it is not improbable that it is in error 

 in this respect also. 



I believe, therefore, that I am justified in regarding the Great- 

 Grimsby Dolphin as a young specimen of the D. albirostris as de- 

 scribed by Van Beneden. 



An interesting feature in the case, however, is the striking resem- 

 blance in external characters which this Dolphin presents to the D. 

 acutus of Gray *. In both there is the same general outline of bodv, 

 massive head, and humped appearance close to the tail ; and in both 

 the sides are piebald, the markings, however, differing in character. 

 Here the similarity ceases ; and in skeletal peculiaricies they diverge 

 widely from each other. The D. acutus has 80 or 82 vertebrae; and 

 in the cervical region the first four are ankylosed together, the first 

 three completely, the fourth simply by its spinous process. In the 

 Great-Grimsby specimen, as we have seen, the vertebrae numbered 

 90, and in the cervical region the atlas and axis alone were fused 

 together. These characteristics, in conjunction with the white snout, 

 are sufficient to show that the Dolphin I have described could not 

 be considered referable to D. acutus. 



It will not be inappropriate to conclude this communication with 

 a brief summary of the various localities in which the recorded speci- 

 mens of D. albirostris have been captured ; and in this way an idea of 

 the geographical distribution of the species may be obtained. 



D. albirostris is a native of the North Sea, but is also found in 



* Gray, Spicil. Zool. 1828 ; Rasek, Nova Species Descripta cum tabulis ii. 

 1843; Duguid, Ann. and Mag. Nat. Hist. vol. xix. 1864; Schlegel, Abhandl. 

 Zool. &c. 1841, tab. i. & ii. fig. 4, tab. iv. fig. 5. 



Proc. Zool. Soc— 1876, No. XLV. 45 



