SCol'ELOIDS. 



923 



eyes and optio iktvcs ai-o entirely aborted, tlie fisli 

 being (■c)Mse(|iieiitl\' (|uite blind". But under tlic ex- 

 tronieh' thin and trans|);u'ent roof of tlu^ skull (an- 

 swerinj;' to the parietal and frontal bones, which are 

 hardlv distinoniisliable), and forward ovei- the wide pa- 

 latine areh, thus extending above ni-arh' the A\iiole 

 surface of the flattened head to the poslerinr limit of 

 the nasal region, there lie a pair of laiuelliforni lumi- 

 nous spots, separated from one anotiier b\' a h)ngi- 

 tudinal median seijtuni rising from tiie root' of the 

 mouth, .\bove each of these huninnus s]iots run both 

 the frontoro.stral Iiraneh of the cephalic s\steni of the 

 lateral line and tlie nasal lu'anch of the fifth jiair of 

 cranial nerves. The jiosition of these luminous spots 

 is thus, like that of the parietal organ, intraqranial. 

 Willi regard td their function Gi'xTHEU remarks: "The 

 power of |iroducing light, and thcreb^■ attracting other 

 creatures, must be of great use to a fish, which, de- 

 prived of organs of sight and touch, would be unable 

 to procure its food." 



As we have mentioned above (p. 826, note/), GCx- 

 theh' has proposed to range the Scandinavian members 

 of this family in two families, the Sternoptychhlce and 

 Scopelidtc. But the difference between these two fa- 

 milies is hardlv appreciable. Thev occu|)\' an inter- 

 mediate position between the Salmonoid and ( 'lupeoid 

 families. In common with the former they possess an 

 adipose tin behind the true dorsal tin, and their ovaries; 

 like those of the latter, are furnished with a special 

 oviduct. The adipose tin is often very small, but in 

 most cases furnished with fibrillous (cartilaginous) rays. 

 The distinction adopted l>v Gunther consists merely 

 in the greater or less length of the intermaxillaries, 

 the posterior part of the margin of the upper jaw being 

 formed in his Stcrnopfi/cJiid(e bv the ma.xillarv liones. 

 Ibit these bones often coalesce so closely with the in- 

 termaxillaries that the limits lietween them can hardh' 

 be detected. The utilitv of tlie character is thus con- 

 siderably reduced. (Jn the other hand it happens, in 

 GCnther's Scopelidce, that the hind part of each inter- 

 maxillary bone is firmly applied to the outer surface 

 of the maxillarv, al>o\e the lower margin of the latter. 

 Consequently the said margin mav form pai-t of the 



margin of the upper jaw in this family as well, though 

 in such instances it is toothless. We therefore prefer 

 the older ojiinion, end>raced in r(;cent times by MoKEAU'' 

 and retain the Scopeloid family in its entirety. It 

 then c<intains about eighty sjiecies of marine fishes, 

 most of them (lee[)-sea forms or nocturnal surface-fishes 

 but some belonging to the littoral regions of the; tropic- 

 seas. The Scopeloids belonging to the Scandinavian 

 fauna mav be dislinguished as follows: 



! : Snout shovtcr than the postorbital 

 part of the head. Dorsal fin situated 

 about liftlf-way along the body. 

 ,4; Abdominal part of the body ex- 

 ceedingly deep and compressed ; 

 its ventral margin sharp and se- 

 parated bv an abrupt break from 

 the under surface of the tail. 



(Subfarailv Sternopti/fhinw) Ari/i/)Vjifli'ciis (H/frsii. 



B: Abdominal part of the body pass- 

 ins uniformly (withoiU sharp 

 break) into the caudal part, and 

 with more or less tiu-ete ventral 

 margin. 



a: Maxillaries f'urni^lied with 

 teeth belHn<l. and entering 

 into the structtne of the mar- 

 gin of the upper jaw. (Sub- 

 family CocciiniK). Preabdomi- 

 nal length greater than the 



postabdominal Maurolicus Midleri. 



h: Maxillaries toothless, and as 

 a rule forming no part of the 

 margin of the upper jaw (Sub- 

 family Sanrinai). Preabdomi- 

 nal length less than the post- 

 abdominal. 



a: Length of the base of the 

 dorsal fin more than ', , of 

 that of the body. Longi- 

 tudinal diameter of the eyes 

 less than ' \ "f t'^c post- 

 orbital length of the head. Myctophum elongatiim. 

 (i: Length of the base of the 

 dorsal fin less than ', g of 

 that of the body. Longi- 

 tudinal diameter of the eves 

 more than ' ', of the post- 

 orbital length of the head. Myctophimi ahtciale. 



2: Snout longer than the postorbital part 

 of the head. Dorsal fin situated far 

 back (Subfamily Paralepidina:). No 

 luminous spots Siidis atlanticus. 



" Also without olfactor}- nerves, according to Moskley. 

 * Cat. Bril. Mus., Fish., vol. V. pp. 384 ami 393. 

 ' Hist. Nat. Poiss. Fr.. tome III, p. 491. 



