1164 



SCANDINAVIAN FISHES. 



tail is of a rounded quadrangular section, and is more 

 or less deepl)' impressed .in the median line above and 

 below. Where the body is shallowest, just in front of 

 the caudal fin, the breadth (thickness) is about ^|^ of the 

 deptli. Tlie greatest depth measures about IS'/g (9) — 

 11' 2 (a^) %, and the least depth about 272—3 %, of 

 the length of the body. The greatest breadth occurs 

 in the head, just in front of the gill-openings, and is 



Fig. 341. Anterior part of the ventral side in a Sngre {Etmopterus 

 spinax), rf, 4 dm. long, from Stromstiid Fjord. Nat. size. 



about 11 — 9 % of the length of the bodv- Across the 

 gill-0])enings, on tlie other hand, tlie body is somewhat 

 contracted, forming, as it were, a neck. 



The length of the head to the first branchial aper- 

 ture measures in full-grown specimens about 17 '/a — 

 17 %" of the length of the body. Above the head is 

 almost flat, underneath convex. Between the eyes the 



forehead is coursed bv a longitudinal gi-oove on each 

 side of a terete median carina, which forks beiiiiid into 

 two divergent branches. The interorbital widtli (in- 

 cluding the dermal rim of the supraorbital margins) is 

 about 4.5 96, and the length of the elongated, anteriorlv 

 and posteriorly pointed orbits about 31 %, of the length 

 of the head. The eyes themselves are also elongated, 

 the height of the iris being about ^4 of its length, 

 which is nearly '/,-, of that of the head. Tlie length 

 of the snout is about equal to that of the orbits, and 

 in form the snout differs considei-ably from that of tlie 

 preceding species, advancing with uniform breadth, 

 until it is abruptly rounded off at the nostrils to a 

 very blunt tip. The nostrils (fig. 341) are apparently 

 double on each side, tlie small, pointed nasal valvules, 

 one from the anterior margin, one from the posterior, 

 laying their tips together, so that each nostril seems to 

 consist of a circular aperture, situated at the very margin 

 of tile snout, ;ind a proximal, oblong opening, directed 

 obliquely backwards and inwards. Their entire breadth 

 (both apertures) is about equal to the distance between 

 their inner extremities, but only '/j of that between 

 the latter and the middle of the margin of the upper 

 jaw, which luargin lies below the posterior margin of 

 the eyes, about half-way along the head. At the middle 

 of the under surface of the snout is a longitudinal con- 

 cavity which calls to mind the groove present at the 

 same point in foetuses of the preceding species. Among 

 the pores belonging to the system of the lateral line 

 on the snout, a double row on each side of the median 

 groove underneath and a similar series on the upper 

 surface, in a loop above the nostrils, are especially pro- 

 minent. At an angle to the last-mentioned series a 

 vow crooks over each eye and is continued back towards 

 the occiput. The broad mouth is .slightly curved, its 

 breadth being about ^ - of the length of the head, or 

 somewhat greater than the distance between the nostrils 

 and the upper jaw. The thin corners of the mouth 

 are each surrounded by a deep groove, which is conti- 

 nued backwards by a slit narrowing to a point. The 

 upper jaw is armed with 3 or 4 transverse ro^\'s of 

 tricuspid or quinquecuspid teeth, with the median cusp 

 largest, one row close behind the other. The lower 

 jaw contains only one row of simultaneously function- 

 ing teeth, essentially similar to those of the preceding 

 species, and forming, as there, a serrated cutting-edge; 



According to Lilljeborq 16 %; according to Kboyek sometimes IS'/j %■ 



