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Show 418 MR. B. W. L. HOLT-STUDIES IN [May *> or arrangement from those of the Common Ling, but the large teeth of the inner row of the mandible and of the vomer, which exhibit the lateral compression and spatulation of the points most strongly, are fewer in number by comparison with Common Ling of the same size; this is due, no doubt, to the latter being considerably younger than the examples before us. The tongue is broad and free, with a sharp anterior edge. There are about 80 pores in the lateral line. Colours.-The dorsal region of the head and body is a brownish slate colour, shading ventrally info a brownish grey on the sides, which have a cupreous lustre in very fresh examples, and becoming nearly white in several examples in the ventral abdominal region. The jaws and under surface of the head brownish grey, the branchi-ostegal membrane not darker than the surrounding region, but the tip of the lower jaw and barbel dark. A dark spot on the axilla ; the pectoral dark slate-grey ; the pelvic pale, but speckled with dark pigment. The dorsals slate-grey, both fins darkest in the submarginal region, especially the posterior part of the second dorsal; the extreme margin light, nearly white in some examples. The anal resembling the second dorsal, but fading into a pale slate colour anteriorly. All these fins have a bluish lustre on their darker parts. The mucous membrane of the mouth may be almost colourless, but is usually rather profusely speckled with black pigment. I a m told that it is sometimes black, but have not seen any specimen to which such description would apply. The peritoneum of the body-cavity dark grey or black. The Birkelange thus differs conspicuously enough from Ling takeu from the comparatively shallow water in our o wn seas; but comparing it with Faroe specimens of that species, I find that the principal difference (so far as concerns external pigmentation) that can be affirmed is that the commoner form is rather the paler of the two. W e know from Lilljeborgl that the two species resemble each other in being more vividly coloured in the young condition than when adult. In order to emphasize the external differences of the two species I have appended a figure of both. The Ling (Plate X X V I I I . fig. 2) is actually some ten inches shorter than the Birkelange (fig. 1), and, the figures being drawn to such scales as to be practically of the same size, the difference in the size of the eyes is not so marked as it would be had examples of the same actual length been represented, since the size of the eye varies in inverse ratio to that of the individual. Nevertheless the eye is seen to be largest in the Birkelange, and its relatively greater length as compared with that of the head is still more conspicuous. Such dimensions as the height of the body and of the caudal peduncle in relation to the total length are practically constant during the interval of size which separates the two specimens, and consequently the value of the figures for purposes of comparison is not thereby impaired. 1 This author (op. cit. iii. Append, p. 787) describes the coloration of an example of M. abyssorum 60 cm. long. |