926 



SCANDINAVIAN FISHKS. 



causes. In front of the dorsal fin the dorsal margin 

 rises in a transyjarciit, fartilagino-osseous carina, re- 

 scnihling an anterior, posteriorly ascending dorsal fin, 

 })ut foi'ined by the |)rodiiced and coalescent tips of 7 

 iieiira.l spines. The ventral mai'gin, on the other liand, 

 is sliarpened at the istlinnis, in the abdominal region, 

 in the region of the anal fin, and just in front of the 

 caudal fin, by the median I'lirina between the rows of 

 luminous spots situated at these points, a structure 

 most nearly corresponding to the \ entral carina of the 

 Herrings. But between the ventral fins and the anal 

 fin tbe ventral margin is chann<;lled by a groove open 

 below. In the rest of their extent the margins of the 

 body are indeed thin, but blunt. The dorsal profile 

 follows a fairly regular curve in front of the true 

 dorsal tin, but from the begimiing of tiiis tin it slopes 

 almost in a straigiit line, until, at the caudal fin, it 

 becomes horizontal. Tlie ventral profile is even more 

 sharply curved in front than the dorsal; but behind 

 the above-mentioned break it ascends at the same angle 

 as that formed by the doi'sal profile in its descent, 

 tliough with a perceptible break at tlie end of the anal fin. 

 The head is deeper tliaii long. Its singular shape 

 i due to the short snout, the vertically ascending cleft 

 of the mouth, and the deep, I)ut short opercular appa- 

 ratus; and to these we should add the comparatively 

 deep isthmian region, which extends under the greater 

 part of the length of the head. At the top the head 

 is convex from the occiput to the snout, but flat and 

 wrooved in the middle, with a sharp, longitudinal ca- 

 rina on each side, and stnmgly constricted between 

 the eyes. Its length in an horizontal direction from 

 the middle of the tip of the snout measures in our 

 specimens about 28 — 21.1 % of the length of the body. 

 The eyes are rather large and round, the vertical dia- 

 meter being only a little greater tlinii or equal to the 

 longitudinal, and varying in our specimens between 

 4;] and \h % of the length of the liead, or about ^ '.^ 

 of that of the body. They are set high, their upper 

 margin rising almost to the frontal plane, and so near 

 to each other that the least interorbital width is only 

 '/j of their vertical diameter. The postorliitaf length 

 is only about ^/j (32 — .34 %), and tlie length of the 

 snout rather more than '/,, (27-28 %), of the length 



of tiie head; and the lower margin of the pupil lies 

 on a level with the tip of the snout or a little higher. 

 The suborbital ring is represented only by an extremely 

 thin, oblong, lamelliforra, and vertically set preorbital 

 bone, which coasts the anterior margin of the eye. 

 The nasal cavities are oblong, and lie close to the an- 

 terior upper corners of the orbits and below the knob- 

 shajied tip (^f the ethmoid bone. Tlie nostrils are di- 

 vided on each side by a thin, but flat septum of skin, 

 «itiiout any elevation of the margin. 



Tiic miiutli ascends almost vertically, and the tip 

 of the up|ici- jaw projects slightly beyond the ethmoid 

 (rostral) tip, but admits of hardly any [irotrusion. The 

 nasal processes of the intermaxillaries are short, and 

 the latter bones, each by means of its lateral branch, 

 are S(j firinh' united to and coalescent with the maxil- 

 laries tliat tlie limit between them is distinct only in 

 front, for a distance measuring about ',., of the dia- 

 meter of the eyes. The motion of the intermaxillaries 

 is thus reduced to a consiilerable extent: they can only 

 follow the forward and backward swing of the niaxil- 

 laries. How far the margin of the upper jaw is formed 

 by the intermaxillaries, it is impossible to determine 

 without dissection, an operation of which our materials 

 have not permitted. But the whole margin of the up- 

 per jaw is set with a row" of pointed, sulnilate and 

 curved teeth, rather scattered and small, but of various 

 sizes. The last four or five teeth' are directed for- 

 wards, the anterior ones jjointing backwards. The ma- 

 xillar\- bone, which is extremely thin, reminds us most, 

 both in shape and structure, of tliat of the Herrings. 

 Just l)ehind (below) the constricted articular part it is 

 curved like a sabre at the very margin of the mouth, 

 but from this point back it is straight and of uniform 

 breadth, forming an oblong rectangle. Tlie median 

 space, however, is not ossified, but consists of a. silvery 

 skin, distended lietween the true maxillary bone and its 

 supplementary (jugal) part, which coalesces behind with 

 the maxillary, and which extends, in the form of an 

 osseous rod, forward to the articular part. The entire 

 length of the maxillary is somewhat more than 4 

 (about 2G— 29 ?i) of the length of the body, and its 

 breadth in the olilong part about '/^ of its own length. 

 The lower jaw is about equal in length to the maxil- 



" Sometimes we fiiul in front, on tlie intermaxillaries, a tooth or two lying inside or outside this row. 



'' Situated on that part of llio upper jaw which, when the mouth is wide open, lies outside the branch of the lower jaw, and thus 

 below the true cleft of the s,n\iv. In Argyropelecus hemigymnus the length of the intermaxillaries may be traced backward to this ponit, 

 whic-h there answers to alxiut llie niiihlle ])oint in the length of the niaxillaries. 



