(wd 



SCANDINAVIAN FIMIKS. 



oxtroiiK' front uf its dorsal |ilani' with two unpaired 

 plates, which have been called occipital, because their 

 middle carina forms a continuation of the occipital 

 carina. These plates also lie so far forward that the 

 auteiior one partly covers the crest of the occiput, and 

 the small gill-openings lie beside the front part of the 

 posterior plate. Thus the hind part of the head with 

 the gill-o})enings lies to a gi'cat e.xtent within the limits 

 of llic trunk. The anterior occipital plate is shorter 

 tiian the ]>osterior, sometimes only half as long. The 

 true occi])ital carina is hardly as high as these so-called 

 occipital plates; but still the occij)ut rises considerably 

 from the forehead, which in its turn slopes forward 

 towards tiic snout. Tlie occiput is also convex, and the 

 sides of the liind part of tlie head are considerably 

 tumid, on account of the alveated form of the oval 

 opt'rcula-. Tliese bones are striated with smooth ridges, 

 radiating upwards and downwards and leaving between 

 them rcjws of small cavities in the surface; and an hori- 

 zontal ridge, granulated by a row of small round tu- 

 bercles and scarcely half as long as the operculum, runs 

 back from the articulation of this bone. The occiput, 

 the tfjp of the head, and the temijles are cavernous 

 in the same manner, but with coarser and more irre- 

 gular depressions. The snout, on the othei- hand, is 

 smooth, with the exception of the bars (carinix>) that 

 follow its dorsal side. One of these bai'S, the dorsal 

 carina of the snout, runs in a line with the occijiital 

 carina, which has terminated and been obliterated on 

 the concave forehead. This bar is coasted on each side 

 b\- another, an immediate continuation in a for\vard 

 dii'cctioii of the strongly elevated ui)per orbital margin, 

 which is continued backwards in the same manner l)y 

 a ridge that runs oblitjuely up towards the beginning 

 of the anterior occipital plate. The orbital margin itself 

 is also continued downwards and sharph' defined in old 

 specimens, in which the ]>ra'frontal l)one also forms a 

 prominent knob at the middle of the anterior orbital 

 margin. All these ridges are granulated at the free 

 rnai-gin, more or less distinctly and most so in old spe- 

 cimens, by a row of small round tubercles. In front 

 of the said pra^'rontal protuberance, ^\'hich is not very 

 distinct in young s])ecimens, lies a triangular depression, 

 Avitliin ^vhich an oblicjuely longitudinal elevation of the 

 skin bears a small round nostril at each end. When 

 the mouth is closed, the snout is somewhat compressed 

 from the sides, with the breadth graduallj' decreasing 

 in front; but when the mouth is open, it is more terete 



and, when seen from above, of more unifoi'in breadth. 

 The tij) of the snout is turned upwards, and rises per- 

 ceptibly above the ascending ti]i of the lower jaw. 



The length of the snout varies considerabh in 

 different individuals, but esjiecialh- according tij age. 

 In Adung s}jecimens, up to a length of 2 dm., it may 

 be oidy slightlv greater or e\en somewhat less than half 

 the length of the head; but in older specimens it mea- 

 sures about 56 — o9 % thereof. The variation is as 

 great, but reversed, in the case of its least depth, which 

 we have found in ^oung .sjjecimens to measure 20 — 18 

 % of its lengtli, while the corresponding proportion in 

 old specimens varies between about 15 and 13 %. As 

 a rule the least depth of the snout is " ., of the length 

 of the lower jaw, which is about the same as the dia- 

 meter of the eyes. The postorbital length of the head, 

 occupied almost entirely by the gill-cover, measures about 

 '4 (31 — 34 %, exceptionally 36 %) of its entire length. 



As we have mentioned above, the branchiostegal 

 membranes are entirely coalescent, below and on the 

 sides, with the front of the shoulder-girdle. The gill- 

 openings, with their crescent-shajjed lids, are small hori- 

 zontal ci'evices, about half as long as the diameter of 

 the e\es, and situated in a line ^vith the latero-dorsal 

 carina' of the trunk, which begin just behind them. 



The only paired tins, the pectorals, occupy an obli- 

 quel}' vertical position about half-way up the body, and 

 ari' of almost uniform lireadth, with sharply rounded 

 ti]). Their rays are simple and unarticulated, somewhat 

 widened at the tip, and usually 12, exceptional]}- 10 — 

 13, in number. The lengtli of the longest (middle) 

 ravs is always less than the depth of the body at the 

 beginning of the tail. 



The dorsal tin begins on the last or the penulti- 

 mate ring of the trunk, at a distance from the tip of 

 the snout wliich we have never found to exceed 39 % 

 (37 — 38',., %) of tlie length of the body, and which is 

 greatest as a rule in the females. It is of almost uni- 

 form height, though it rises slightlv in a backward direc- 

 tion for about three-fourths of its length and then sinks 

 again. Its rays (usually 35 — 42, exceptionally 43 — 45), 

 like those of the other tins, are simple and unarticulated; 

 thcA' are somewhat broader at the tip and compressed 

 (flattened in the longitudinal direction of the body). 

 It more or less entirely occupies 10 or 9 rings of 

 plates, and the length of its base, which is always 

 shorter than the head, measures 11 or 12 % of that 

 of the body. 



