416 MB. E. w. L. HOLT — STUDIES IX [May 1, 



of the body. The length of the eye, greater than its height, con- 

 tained about five times in the length of the head, and once and a 

 half or nearly twice in the length of the preorbital region. The 

 len<jth of the eye aluai/s greater than the width of the intero7'hital 

 space, which is usually less than the height of the eye, but may be 

 equal to or even a little greater than that measurement. The 

 lower jaw the longer, projectiug hei/ond the snout, the barbel small, 

 much less than the length of the e3''e. 'The height of the caudal 

 peduncle less than the height of the eye. The vent opposite about 

 the seventh or ninth ray of the second dorsal. The mouth more 

 or less closely speckled with black ehromatophores. 



The italics are intended to denote such characters as serve at a 

 glance to distinguish this species from the Common Ling (J/. 

 vulgaris, Tlemiug), and the close resemblance which the Birkeliinge 

 bears to that \i-eU-kuown form renders it unnecessary to elaborate 

 the diagnosis further. 



The diagnosis is based on the examination of the seven specimens 

 forming the subject of this note, which range in total length from 

 42 to 50| inches. Hence it may not be strictly applicable to 

 smaller examples, since the proportions, especially those of the eye, 

 are subject to developmental changes in all fish. I am led by this 

 to suppose that Lilljeborg, who describes the iuterorbital space as 

 much less than the height of the eye, may have based his remarks 

 on the examination of smaller fish ; but it is quite possible that a 

 variation iu this, as apparently in some other respects, exists 

 between Scandinavian and more Western examples of this species. 



The condition exhibited by my specimens renders it also probable 

 that the relative length of the lower jaw increases \^ith the size of 

 the fish, so that in young examples it may even be less than that 

 of the upper jaw'. We know this to be the case in the Coal-fish 

 (Gadus virens), in which the lower only passes the upper jaw when 

 a length of about twelve to fifteen inches has been attained. 

 There remain, however, other characters sufiiciently well marked 

 to distinguish the species at any size. The Birkelange is not 

 known to reach a length greater than 60 inches ■, and is therefore 

 a much smaller fish than the Common Ling. 



^ It may be remarked that very large Common Ling occasionally exhibit an 

 infinitesimal projection of the lower jaw. Sucli a projection is given by Lillje- 

 borg as a specific character in the case of the species before us. Smitt, however, 

 states that in all his specimens the ujjper jaw was distinctly the longer, and his 

 figure (o^j. cit. pi. xxvi. fig. 3) shows this condition clearly enough. From 

 internal evidence the material forming the subject of his remarks seems to have 

 consisted of four examples, stated to be adult, ranging in size from 56'2 to 

 828 cm., and therefoie all smaller than our Iceland and Paroe specimens. It 

 is, nevertheless, by no means clear that all small examples have the snout pro- 

 jecting, as Lilljeborg {op. cit. iii. Append, p. 787) mentions an example of 

 60 cm. without qualifying liis pi-evious remarks on the conformation. On the 

 whole it seems most probable tliat the majority of adults, whether from Scan- 

 dinavian or other waters, haye the lower jaw the longei*. 



- Smitt {op. cit. p. 522) observes that the species seldom exceeds a length of 

 one metre (39 inches ca.), but it does not appear that his acquaintance with 

 this fish is very extensive. 



