CnUASSKD {;ri!XAI!l)S. 



203 



(iiii'iiiirds. But the absence i>t' the ;iir-l)hHld(M', the 

 undivided pectoral tins without tree rays at the bottom, 

 the somewhat siiii^ular forin of the bod\', and the situa- 

 tion of the vent, which lies tar in I'ront nf the end of 

 tlie abdominal ravitv, nearer the Neutral lius than the 

 anal tin, are all in I'aNour of I he in'ocednrc oi' Gill", 

 and aftei' hiiu of -Ioriian and ( in.i!i;i;i'''. who isolated 

 these fishes under the fainih name of Af/aitidir, which 

 was tirst emploxed by Swainson'. TIh' body is of the 

 typieal Cottus foi'ui, witii the head thicker than the 

 body, which tapers posteriorK- in ii conical form, but 

 is sometimes so elongated and low that, with its few 

 rows of jdates, it i-eminds us of the Si/ni/nathl. Its 

 resend)lance to the latter is furtlier increased by the 

 longitudinal cur\ature of the plates on the trunk, which 

 are traversed b}' a keel at the middle, on the outside of 

 the curve. Sometimes, too, as in the genus Slphagonus, 

 the snout, with the projecting lower pw, is almost tu- 

 bular and resembles that of Si/i/f/nafhus. Sometimes, 

 how^ever, as in the genus Botliragonus, the body is 

 laterallv more strongly compressed and fairly deep and 

 short. The variations of form within the family are 

 thus h\ no means inconsiderable. The eyes are set 

 hiiih, but on the sides of the angular and lacunose 

 head; and on the lower ])art of the clieek we tind the 

 row of muciferous ]X)res, belonging to the system of 

 the lateral line, \\hicli wg have remarked aljove in the 

 fr\- of the Sapphirine Gurnard. The strange appearance 

 of the head is often enhanced bj^ the elongation of the 

 snout into a kind of proboscis, and by the spines on the 

 upper surface of the latter; and numei'ous barbels are 

 sometimes attached to the lower side of the head. 

 Behind the fourth branchial arch the gill-slit has dis- 

 appeared; and the pseudobranchiie are well-developed. 

 Tlie jaw-teeth are small and cardiform; and similar 

 teeth sometimes ot'cur on the ])a]atine l)ones and the 

 vomer as well. The ventral tins, with one spinous and 

 two oi' three soft raj-s, are set fairlv close together 

 and somewdiat behind the insertions of the pectoral fins. 

 As a rule, there are two dorsal fins, the anterior \vith 



spinous rays; but sometimes, in the genus Aspidopho- 

 roi(les'\ tliis last fin is wanting. 



The sj'stematical, as well as the morphological, 

 relations between the genera are explained, in this fa- 

 mih- as in others, by the changes of growth in the 

 species, which changes have already been descril)ed by 

 Steenstkup and LOtken'". The most remarkable of 

 these changes is the gradual removal in a forward 

 direction of the \ent — in a specimen of Afjonus de- 

 canouns, 76 mm. long, from Greenland, we find 8 pairs 

 of ])lates between the vent and the l)eginning of the 

 anal fin, in another, 162 ram. long, 10 plates on the 

 left side and 11 on the right; in a specimen oH A(/oni(S 

 cataj)Jiracfi/s, 93 mm. long, from Bohusliin, there are 

 f) ])lates on the right side and 6 on the left, between 

 the \ent and the anal fin, in a specimen 121 mm. long, 

 6 on each side, and in a specimen 178 mm. long, 7 

 pairs of plates on this space. Another change lies in 

 the elongation of the tip of the snout, and the eleva- 

 tion, or even tiie protrusion, of the nasal spines. Young 

 specimens are without the marked elongation of the 

 nasal bones in a, forward direction, in front of the 

 original tip of the snout, or even (as in Af/onus dccafjo- 

 fius juv. = Af/. spinosissimns) have the lower jaw more 

 protruded than the upper. The form of the body in 

 these species begins its changes with the relativeh' 

 shorter (deeper) form in young specimens than in old, 

 and with the deeper caudal region, which is even la- 

 terally compressed. In young specimens of both tlie 

 Scandinavian species of Agonus, the middle keels of the 

 plates on the body and the ridges of the head are 

 higher, and I'ise into spines pointing in a backward 

 direction, even in the species {Ag. cataphractus) which 

 in the adult state can scarcely be called spinous, so 

 rounded and blunt have these plates and ridges become. 

 The genera which, when full-groAvn, are distinguished 

 by the deeper form of the body, by higher spines on 

 the plates, b\- the shorter (more obtuse) form of the 

 tip of the snout or by the rising (projecting) tip of 

 the lower jaw, ma^• thus be regarded as representatives 



" Arrang. Finn. Fish., Smiths. Misc. Coll. Nu. '247, y. 0; Cat. /-Vs/i. E. Cort.-'f -V. Aviei:. ibid.. No. 28.5. p. 2. 



* Sijii. Fisii. N. Amer., Bull. U. S. Nat. Miis., No. 16, p. 722. 



' Nat. Hist., Class. Fisli. Ampli.. Rept., (Lardn. Cab. Encycl.), vol. II, pp. ISl and 272. 



•^ One species of this genus. A. Olrikii, has been found both in Greenland and in Kara Sea (LCtkex in Dijmphna-Togtet, \>. 120), 

 and may possibly occur, therefore, in the deep water off the extreme north of Norway, though it is just as probalde that its range extends 

 west only from Greenland to Nova Zembla. .\ specimen do mm. in length, was taken by the Vega Expedition at a depth of 18 fathoms, 

 in Behring Strait (64° 52' N. ; 172° 3' W.) 



' Via. Moddcl. Naturh. I'^or. Kbhvn 1S61, p. 276. 



