572 



SCAXDIXAVIAX FISHES. 



extend nearly tu its extrcniit}-. The opercular appa- 

 ratus as a wliole is fairly large, but the operculum 

 proper is the smallest part (about Vs) thereof. The 

 operculum is smooth, convex, triangular, and almost 

 equilateral. The greatest part of tiie oi>ercular apparatus 

 consists of the suboperculum, wliich forms the whole 

 of the inferior and posterior parts, and with its broadly 

 rounded point projects somewhat behind and above the 

 base of the pectoral fin. It is united to the operculum 

 by an obli(pie, straigiit line; tlie lower margin forms 

 a large, rounded sinus, to receive tlie base of the pec- 

 toral fin; and the surface is smooth, with 9 distinct, 

 radiating lines on tlie lower part. The four branchial 

 arches are complete, and a well-developed pseudobranchia, 

 composed of from 12 to 14 threads, occupies tlie inner 

 surface of each gill-cover. 



On the body itself we observe several longitudinal 

 lines, first the lateral line proper, which lies higii on 

 the back, the distance between it and the dorsal tin 

 being about V2 oi' that between it and the median line. 

 The lateral line is parallel to the dorsal fin, straight, 

 and depressed in the rather large scales, each of which 

 contains a branch of the rauciferous canal Avitli its 

 opening. The line begins above the gill-cover, without 

 its usual external continuation on the head, and ends 

 at the termination of the dorsal fin. — Along the middle 

 of the sides there runs a somewhat depressed median 

 line along the middle angles formed by the aponeurotic 

 septa of the large lateral muscles. This line is quite 

 straight and consists of rather small dots, pricked, as 

 it were, with a needle, and invisil)le without tlie help 

 of an ordinary magnifj'ing-glass. They form an irre- 

 gular double (or multiplex) row, equal in width in half 

 a scale. The line resembles a lateral line, l)ut is less 

 marked and destitute of muciferous ducts. — ( )n the 

 sides of the belly we find a still more remarkable carina 

 or dermal fold, which begins below the base of the 

 pectoral fin, follo^vs a perfectly straight course, and gra- 

 dually disappears half-way between the vent and tiie 

 caudal fin. Its height is about equal to the greatest 

 breadth of a scale; it is thin and soft, and does not 

 seem to contain any muciferous canal; but, in speci- 

 mens preserved in spirits at least, it lies with the free 

 margin bent outwards, covered l)y the mucus of the 

 skin, and thus appears itself to surround a canal. — On 

 the belly, between the two lateral carina?, three fine 

 longitudinal lines run from belo'w the pectoral fin to 

 the vent, the t^vo lateral ones slightly depressed, but 



the middle one verv fine, somewhat raised, of clear 

 colour, and scaleless. In middle-sized specimens the 

 anal aperture lies at the end of the third fifth of the 

 length of the body, in the largest specimens a little 

 farther back, its position thus growing more posterior 

 with age. It is only slightly, if at all, prominent, 

 hardly more so tiian the smaller opening for the genital 

 organs that lies behind it. 



The dorsal fin is of almost uniform height, its 

 height in large specimens being scarcely- half the depth 

 of the body. It begins at tlie end of the first fourth 

 of the body, or usually a little farther back, about as 

 far (in young specimens somewhat less, in old somewhat 

 more) behind the occiput as the latter from the tij) of 

 the snout. It ends some way from the caudal fin, the 

 distance between them being about equal to the least 

 depth of the tail, or a little greater. The rays are 

 about 56 in immber, the variations being appai'ently 

 confined to 2 or 3 more or less; all the rays are fine 

 and articulated, but perfectly simple and pointed though 

 not pungent. The membrane is thin and fragile. 



Tlie anal fin begins just behind the genital opening 

 and ends opposite to the termination of the dorsal fin. 

 It is equal in height to the latter, and contains aliout 

 30 rays of the same structure as those of the dorsal fin. 



The caudal fin is deeply forked; its greatest length 

 is about equal to the dejith of the body. It contains 

 15 true (articulated) rays. Thirteen of these are bran- 

 ched, though not very deeply, the outermost ray above 

 and below being simple and only slightly shorter than the 

 corners of the fin. Outside these rays there lie several 

 small, unarticulated or supporting rays: in a specimen 

 3 dm. long Sundevall counted 1 1 aliove and !• below. 



In middle-sized specimens the pectoral fins do not 

 extend further liack than to the jierpendicular from the 

 first ray of the dorsal tin. In the very largest speci- 

 mens they are relatively much shorter. In the speci- 

 mens mentioned above, between 1 1 and 28 cm. long, 

 the length of the jiectoral fins varies with increasing 

 age between 9 and 6' g % of that of the Ijody, from 

 33 to 22 % of the distance between the dorsal fin and 

 the tip of the snout, or between 81 and 56 % of the 

 postorbital length of the head. They are also invariably 

 shorter than the lower jaw, tlieir length varying with 

 increasing age in the .said specimens between 88 and 

 64 % of that of the latter. They contain 14 rays, all 

 articulated; the first is simple and measures only slightly 

 more than half the length of the fin, the second is in- 



