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Show 416 MR. E. W. L. HOLT-STUDIES IN [May 1, of the body. The length of the eye, greater than its height, contained 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 length of the eye always greater than the width of the interorbital 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, projecting beyond the snout, the barbel small, much less than the length of the eye. 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 chromatophores. The italics are intended to denote such characters as serve at a glance to distinguish this species from the C o m m o n Ling (M. vulgaris, Fleming), and the close resemblance which the Birkelange bears to that well-known 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 5 0 | 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 a m led by this to suppose that Lilljeborg, w h o describes the interorbital space as much less than the height of the eye, m a y have based his remarks on the examination of smaller fish; but it is quite possible that a variation in this, as apparently in some other respects, exists between Scandinavian and more Western examples of this species. The condition exhibited by m y specimens renders it also probable that the relative length of the lower jaw increases with the size of the fish, so that in young examples it may even be less than that of the upper jaw1. W e 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 sufficiently well marked to distinguish the species at any size. The Birkelange is not known to reach a length greater than 60 inches2, and is therefore a much smaller fish than the C o m m o n Ling. 1 It may be remarked that very large Common Ling occasionally exhibit an infinitesimal projection of the lower jaw. Such a projection is given by Lilljeborg as a specific character in the case of the species before us. Smitt, however, states that in all his specimens the upper jaw was distinctly the longer, and his figure (op. 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 therefore all smaller than our Iceland and Faroe specimens. It is, nevertheless, by no means clear that all small examples have the snout projecting, as Lilljeborg (op, cit. iii. Append, p. 787) mentions an example of 60 cm. without qualifying his previous remarks on the conformation. On the whole it seems most probable that the majority of adults, whether from Scandinavian or other waters, have the lower jaw the longer. 2 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. |
