156 



and without accessory plates. Maxillae I and II are usually normally 

 developed but in Acanthoscina the palp of maxillae I is absent and the 

 lobes of maxillae II are fused. The outer lobes of the maxillipeds are 

 weakly armed, sometimes reduced to small plates; the inner lobes are 

 rudimentary and always fused, or sometimes absent. Coxal plates VI-VII 

 may be fused with the pereon somites. The pereopods are long and 

 slender, usually simple, although sometimes pereopods I may have a 

 poorly developed chela and pereopods V a subchela. Pereopods V-VII 

 may have retractile claws. Pereopods V are usually the longest of all the 

 pereopods but sometimes are shorter than pereopods VI. The uropods 

 have fused basi- and endopodites; exopodites I and II and sometimes 

 also uropods III are reduced to small spines. The telson is small and 

 short. 



Among the Hyperiidea, this family is the richest in species. It is 

 distributed in all regions of the world ocean from the Arctic Basin to 

 the Antarctic. The scinids are the most characteristic members of the 

 meso-, bathy-, and abyssopelagic zones. Evidently, only a small number 

 of species have secondarily adapted to living in surface waters while at 

 the same time retaining their deepwater features. The scinids are either 

 depigmented'or reddish-violet or bright red (mesopelagic species). Some 

 species are capable of phosphorescence. Most scinids, judging from their 

 stomach contents, feed on tissues of deepwater coelenterates. 



The long and strong, forwardly directed antennae I are noteworthy; 

 they are attached to the upper anterior angles of the anteriorly straightly 

 truncated broad head. Together with the narrow pleon and a compara- 

 tively broad pereon they (antennae I) impart a horn-like appearance. 



The family includes four genera. 



KEY TO GENERA OF FAMILY SCINIDAE 



1. Body without dorsal spines and denticles. Pereopods without retrac- 

 tile claws and fused segments 1. Scina Prestan. 



— At least some somites of pleon and pereon with long dorsal denticles 

 or spines. Pereopods V-VII with retractile claws or distal segments 

 of pereopods V fused 2. 



2. Outer lobes of maxillipeds reduced to two small rectangular plates; 

 inner lobes absent. Fourth, 5th, and 6th segments of pereopods V 

 fused 4. Acanthoscina Vos. 



— Outer lobes of maxillipeds not in form of small rectangular plates; 

 inner lobes present. Fourth, 5th, and 6th segments of pereopods V 

 not fused 3. 



134 3. First two somites of pereon fused. Inner lobes of maxillipeds reach 

 1/3-1/2 length of outer lobes. Pereopods III-VII with nonretractile 



