Lagenorliynchus albirostris. Oray. 





'ince Gray's and Bi-ightwelTs descriptions ut' this species of Dolphin, about 50 years ago, acquaintance with its external 

 appearance and skeleton has lieen considerably extended. There exist many representations of the full-grown animal, which, 

 however, are remarkable for their disagreement in point of colour, an evidence of the numerous variations in this species, in 

 that respect. The full-grown male, according to P. J. van Ben eden, attains to a length of 3 metres, while the females 

 are somewhat smaller. After James Grieg's measurements, the largest female that was observed, in the Whale-take 

 on Bildoen near Bergen in 1887, was 2.74 metres long, while the largest male measured 2.98 metres in length. 



This species of Dolphin occurs not infrequently on both the north and south coasts of Norway. Subfossil remains 

 of it have been found (Guldberg 108), and, during the last decade, "schools" of ,, \Vhite-beaks" have been taken on the 

 west coast of Norway (cf. Grieg 117). 



Fætuses of this species have been described by Liitken and James Grieg. Sven Nilsson (89) mentions a 

 IV2 feet long fætus from a female which had run on to a sand-bank between Skanor and Hammar (Sweden). 



Professor Liitken (116) describes 2 fretuses of Lagenorhynchus albirostris, a male 790 millim. and a female 

 700 millim. in length, and subjoins a table of measurements. These fætuses possess most of the specific characters, and must 

 be placed in the class which I have designated as "almost full-grown". 



James Grieg gives the exact measurements of the three albirostris foetuses which have been at my disposal for 

 the present investigation. The largest measures 1130 millim., the two others 765 and 720 millim. respectively. 



The largest foetuses, 1130 millim., I agree with J. Grieg in classing as "full-grown". As the largest female 

 measured was 2.740 metres (J. Grieg) it will not come far short of the truth if we take the length of the newly-born animal 

 to be Vt of that of the mother. It would undeniably have been of great interest, if the female from which the embryo was 

 taken had Iteen measured. 



The examination of these large fætuses is of interest, inasmuch as they amplifly and substantiate the results 

 furnished by L. acutus, viz. that the specific characters appear distinctly, beginning by degrees to assume their definite 

 form, as soon as the fætus has attained to half the size of the newly-born animal. 



I. The smallest of the above fretuses which I examined was a female, and measured 720 millim. in length 

 Its diminution in length, after having lain in spirit for about four years, proved to be exceedingly slight, viz. less than 

 lU milHm. In comparing it with tlie fætuses of Lagenorhynchus acutus, it must be classified as "almost full-grown,, 

 as it lueasures about 73 of the length of the full-grown young. The length of the head is contained hardly 4'/- times in 

 that of the body, the pectoral fins amount to more than 'A-/, i/A.iO of the length of the body (Ve in the full-grown animalj, the 

 height of the dorsal fin is more than '/n (Vn.*), and the width of the tail fin 'A of the length of the body. 



The head is of a rounded, conical form, with a distinctly marked-oft' "beak", upon the front end of which 

 may be counted 4 fætal hairs. The upper lip describes only an extremely slight sigmoid curve, with a convexity in 

 front. The edge of the lower lip forms a downward-turned concavity with a keel within. In the jaw, the teeth are about 

 to break through. The anteriorly free tongue has a crenulated edge. The deep groove which separates the beak from the 

 rest of the facial part is interrupted at tlie median line, but is deepest at the sides, becoming shallower and finally disappearing 

 in front of the angle of the moutli. 1'lie region of the eye is very prominent (the reverse of that in L. acutus) and is situated 

 a little above, and about 2 centuu. beliind the angle of the mouth. At a similar distance behind, and a little lower than 

 the eye fissure lies the little ear aperture, in appearance like a whitish dot, of the size of a pin's head. The nasal 



