468 Survey of Fishing- Grounds, West Coast of Ireland, 1890-1891. 



hind wall of the orbit. Here again we find the young exhibiting a closer 

 resemblance to adults of another species (in this case M. Bairdii) than to their 

 own, though the gradual transition of the character throughout the series leaves 

 their specific identity in no doubt. In yet another character we find the young 

 presenting a close resemblance to adults of other species, viz. in the direction of 

 the posterior margin of the pre-operculum. In the larger specimens of M. cBqualis 

 {cf. fig. 1, or Giinther, loc. cit., fig. C), this scute is almost vertical in its 

 posterior outline, whereas in M. sclerorhynchus and M. Bairdii it is decidedly 

 oblique. It is equally oblique in our specimen D, but becomes more and more 

 upright as the size increases. It is a feature which is, of course, connected with, 

 and directly dependent on, the forward rotation of the mouth, in the greater 

 extent of which M. cequalis may be said to exhibit a less degree of specialisation 

 than the other two species. 



The proportion borne by the head and trunk to the total length is rendered 

 in this, as in many other species of Macrurus, of small importance, on account of 

 the frequent mutilation of the extreme caudal region, especially in large examples. 

 Both X and A [cf. fig. 1) seem to have lost some part of the end of the tail, as 

 the latter terminates rather bluntly, but the proportions are much the same (head 

 in total length, X6^, A 6-rV ca.) in both examples, and may be representative of 

 the condition usual in adults. Specimen B is obviously mutilated, and exhibits 

 the simulation of a caudal fin so well known in this genus ; but C and D appear to 

 be perfect, the tail terminating in a long, slender filament; the length of the 

 head, however, is contained in the total length not quite six times in C, and over 

 seven times in D, so that either the variation in this feature is considerable, or the 

 caudal filament in one specimen is in reality imperfect. 



Dr. Giinther has described in M. rudis, a species stated to be very closely 

 allied to that now under consideration, a regular developmental change in the 

 position of the vent, from a point near the origin of the pelvic fins in the young 

 to one much nearer the commencement of the anal fin in old examples. It follows 

 that the proportion borne by the distance between the vent and isthmus to the 

 length of the head increases with the growth of the fish.* No evidence of a 

 similar developmental migration in M. cequalis is afforded by our series ; but it 

 does appear that the vent is subject to a rather extraordinary irregularity in 

 position, though its relationships to the pelvic fins are practically constant. The 

 distance between the vent and the isthmus in terms of the length of the head is 

 for X '55, A -58, B "54, C '60, and D '53. The first dimension therefore seems to 

 vary from about five- to six-tenths of the last, without regard to the size of the 

 individual. 



A character given by Dr. Giinther, in his description of the "Challenger" 



*■ Op. cit., p. 132. 



