TETRAGONURUS ATLANTICUS. 137 



Thus a considerable space, nearly equal to the length of the head, or one fourth of 

 that of the body, is left between its hinder end and the root of the caudal fin. It 

 consists of eleven rays, of which the two or three first are simple ; and the fourth 

 is the longest. The last ray nearly equals half the length of the fourth. All of 

 them are soft, distinctly barred, and very fragile ; being of a substance like whale- 

 bone. 



The anal fin corresponds in structure, form, and termination, precisely with the 

 second dorsal ; but begins a little backwarder, and is altogether lower and smaller. 

 Its last ray is the length of the fifth or longest ray. The two first rays are simple. 

 Though the bases both of the second dorsal and the anal fins are not seated in a 

 proper groove, the scales rise a little on each side. The web of these fins is how- 

 ever perfectly naked. The last ray of both is free behind ; and not double as 

 usual, but branched like the preceding. There are no spurious finlets behind 

 either ; but the last ray of each is a little produced or apiculate, as in most fishes. 

 The two dorsal fins occupy a middle space on the back, rather greater than one 

 third of the length of the body, from the tip of the muzzle to the termination of the 

 lateral line or point of the scaly part in the middle of the caudal forks : leaving a 

 space before the first ray of the first dorsal fin exactly equal to that behind the last 

 ray of the second. 



The caudal fin is large and forked, with the lobes broad but rather short ; the 

 upper one being the largest. Their outer base both above and beneath is raised or 

 convex (as is usual in Scombridce) by a number of short accessory rays : and all 

 the rays, like those of the second dorsal and the anal fins, are extremely fragile, of 

 a whalebone-like substance, and strongly barred or knuckle-jointed, as in Alepi- 

 sanrus. From their fragility, the points of the lobes can rarely be preserved 

 entire. They are in length about equal to the greatest depth, or one seventh of 

 the whole length of the fish. 



The whole body, the opercles, and the cheeks are covered with a peculiar kind 

 of hard and compact armour of large close-set scales, elegantly and beautifully dis- 

 posed, like neatly-plaited braids of hair, in regular oblique subspiral rings, or arcu- 

 ated lines, descending oljliquely forwards from the dorsal to the ventral edges. Of 

 these lines there are eighty-three from the origin of the lateral line on the shoulder 

 to that of the upper of the two keels at the root of the tail-fin, beyond which they 

 are confused and indistinct : on the opercle there are ten, and nearly the same 

 number on the preopercle. At the root of the tail-fin and on the nape these rings 

 or rows of scales are consideral)ly narrower : but on the sides of the body they 

 preserve great uniformity of size. On the caudal keels the scales rise abruptly 

 into jagged or ragged crests : and they are continued over the whole breadth of the 

 caudal fin in the middle of its forks to the tip of its shortest ray into a point, 

 exactly as in Beryx. To this point, which is the termination of the lateral line, 

 the two keels converge : and the scales of the fleshy part thus intercepted by them 

 on the caudal fin are quite small and confused. They are all so firmly fixed that 

 they can scarcely be removed without laceration ; tearing off in spiral belts, and 

 adhering strongly laterally to each other. The exposed part of all the scales is 

 exactly rhomboid, and strongly longitudinally striate, with the edge also finely 

 pectinato-ciliate. Examined with the compound microscope, these striae are 

 found to be composed of rows of distant imbricated spines or teeth ; the angles be- 

 tween which, laterally, are not acute as usual, but widely arched or rounded. 

 The outer edge of the scale is deeply pectinate or scalloped ; and the whole 

 resembles a Pecten, with imbricato-spinose ribs. Hence the surface is very rough, 

 when the finger is drawn from the tail forwards : though it is peculiarly smooth, 

 and has a silky feel to the touch, when the hand is passed in a contrary direction. 

 The lateral "line is nearly straight ; descending very gradually to the middle of 



