KATIIEH-LASIIKK. 



189 



fish ex|);iii<ls tlie gill-covers, an opci'iifion usualh' acroiu- 

 |ianied hy a grating noise", and resorted to by the iish 

 as soon as it is di-aAvn out of the water, tiiese long spi- 

 nes point upwards and outwards, in a w.w which gives 

 them some resemblaiu-t; to a pair of horns, i'^rom this 

 circumstance has arisen the name of Ox-sinipa {bnbrdis). 

 Besides the K)ng spine, a third part of wliich generally 

 projects out of the surrounding skin, the margin of the 

 preoperculuin is furnished with three smaller spines, 

 which vary in form, hut seem to he alwa\s pirseut: 

 the lowest ol' them is turned downwards and forwards. 

 The suboperculum is fui'uished witii two or three 

 }jointed spines. Another character which distinguishes this 

 species, is the circumstance that, from the margin of 

 the skin which is united to the upper part of the eye, 

 and wiiich i-esembles an eyelid, there hang down over 

 the margin of the iris iive or six small, thin, dermal 

 filaments, the next to the last beiu": twice as long- as 

 the others and, during life, erected vertically upAvards''. 

 A similai', though mucli longer, dermal filament — oi- 

 sometimes two — appears at tlie trioleate end of tiie upper 

 jaw-bone''. The branchiostegal membrane is interiorly 

 united to the isthmus, without a free fold across the 

 latter. The course of the lateral line is fairly straight 

 and forms no curve in its posterior part. It is gene- 

 rally armed with stiff points, which are anteriorly set 

 in large munbers on the small, slightly raised, scaly 

 disks which form the line, but gradually diminish in 

 number posteriorly and, as a rule, completely disappear 

 at the end of the second dorsal tin'. The scattered, 

 pointed, scaly plates with which the sides of the Sea 

 Scorpion are furnished, are entirely wanting in this spe- 

 cies in its adult state; but it passes through a larval 

 stage, so to speak, during which it has pointed, scaly 

 spines on the anterior part of the body, both above and 

 below the lateral line. These spines have disappeared, 

 however, when the fish has attained a length of 26 

 nun.'', and the somewhat granulated skin is subsequentlj^ 

 quite unarmed and covered with a clear, thick mucus. 

 The tAvo dorsal fins are ijuite distinct, but often only 

 imperfectly separated from each other. The membrane 



of tlie anterior tin is often united to the base of the 

 first ray in the second, higher up in some specimens 

 than in others, in the first dorsal tin there are gene- 

 rally 8 rays, but sometimes only 7, the two first being 

 usually closely joined at the base; in the second from 

 10 to 12 and sometimes Ki. The anal fin contains 8 

 or 1) I'aA's and sometimes 10. The pectoral fins, in 

 which there are 14 or 15 rays, are completely without 

 the serrate ridges wliich ai)])ear on the inside of the 

 rays in the Sea Scorpion. This is also the case with 

 the \entral fins, which li;i\e one, shoi't, spinous i-a\', 

 hidden by tlie skin, and tin-ee simjde, articulated rays, 

 the middle one being the longest. The caudal fin con- 

 tains from 12 to 14 rays, from 7 to 9 of tlie middle 

 ones being branched at the tip. 



In external form the difference lietween the .sexes 

 is less striking in this species than in the pi'eceding 

 one. The iihiIc may be recognised, however, by the 

 more slender l)ody, the larger spines on the head and 

 the elevation of the anal region into a long, conical 

 papilla. As usual, lunvever, its chief external distinction 

 li(^s in the greater length of the fins, especially of the 

 ventral, which in this sex, at least when the fish is 

 over 60 mm. in length, apparently vary between 16 

 and 20 % of the length of the body, and in ordinarv 

 cases extend as far back as the vent or even farther. 

 The base of the anal fin, too, is generally longer in the 

 male, but the distance between the insertion of the 

 ventral fins and the beginning of the anal tin is less 

 in the male than in the female, a circum.stance which 

 gives us the general rule that, in the male the base 

 of the anal fin is at least 80 % of this distance, in the 

 female at most 76 96. Further, in those resjjects in which 

 distinct changes of gro\vth appear, the male represents, 

 in this species also, the lowest stages of development, 

 e. g. in the size of the eyes (see the table below). 



The difference between the sexes is more apparent 

 if Ave observe the coloration, though it is extremely 

 variable. Our plate gives the colouring of both sexes 

 as it usually appears (the originals are from the Baltic). 

 The prevalent green colour is a distinguishing mark 



" According to Sorknsk.n (Oin Lijdorganev hos Fide. Kbhvii 1884, p. 79) this sound originates at the articulation of the preoperculuin 

 witli the hyomandibiilar bone. According to DuFOSSE (Ann. Sc. nat., ser. 5, Tome XIX et XX — 1874), we may conclude that the vibration in 

 the articulation, wliich is the immediate cause of the sound, is due to the vibration of the muscles of the hyomandibular apparatus which in these 

 muscles, as in all others, accompanies their strongest possible contraction. This sound also occurs, though there it is weaker, in the preceding species. 



' Cf. above, on Centridermichthys liamatus. 



■ In a sprcimcn 71 mm. in length from Wnidcgnba (Kola Peninsula) tlie lateral line is without any spine whatever, except the stiff 

 margin of the middle pores, which is raised in a posterior direction. 



"^ Cf. XIai.m and Collett. 



