158 



The characteristic features of each of these groups are given below 

 in the descriptions of individual species. 



Most of the species of Scina are deepwater forms, living in meso- 

 and bathypelagic zone, i.e., in depths from 200-500 to 3,000 m; only a 

 few species live exclusively in the abyssopelagic zone, i.e. deeper than 

 3,000 m, or inhabit surface waters. Such surface-dwelling Scina species 

 are found only in the warm water regions of the ocean. 



1 35 KEY TO SPECIES OF GENUS SCINA 



1 . Pereopods V: 4th segment nearly same length as 5th, sometimes 

 shorter than or only slightly (not more than 25%) longer than it . . . 

 ....2. 



— Pereopods V: 4th segment much longer than 5th 21. 



2. Pereopods V: 6th segment thin, weak, and short, less than half 5th in 

 length. Large species with antennae I exceeding pereon in length . . 

 3. 



— Pereopods V: 6th segment half or slightly more than half, equal to, 

 or slightly longer than 5th. Species generally smaller, with variable 

 length ratios of antennae I and pereon 6. 



3. Pereopods VII: 6th segment equal to or longer than 5th 4. 



— Pereopods VII: 6th segment shorter than 5th 5. 



4. Pereopods VI: claw long, almost straight; 4th segment almost equal 



to 6th, each of them slightly longer than 5th 



1 . S. crassicornis (Fabr.) 



— Pereopods VI: claw very short and falcate; 4th segment roughly 1.5 

 times longer than 5th or 6th 2. S. curvidactyla Chevr. 



5. Pereopods V: anterior and posterior margin of 2nd segment smooth 

 or, in an extreme case, anterior margin at base of distal process with 

 some denticles 11.5. stebbingi Chevr. 



— Pereopods V: 2nd segment denticulate along entire posterior margin 

 and finely denticulate along entire anterior margin; large denticle 

 present only in its distal part. Second segment of pereopods III, is 



2/3 length of 4th and 5th segments together 



3. 5. curilensis Vinogr. 



6. In pereopods I or in pereopods I and II, 6th segment extended over 

 claw in form of a small distal denticle 7. 



— In pereopods I and II, 6th segment without distal denticle 9. 



7. Pereopods VI-VII: 6th segment longer than 5th. Outer lobes of max- 



illipeds stretched, more than 5 times longer than inner lobes 



4.5. incerta Chevr 



— Pereopods VI-VII: 6th segment shorter or equal to 5th. Outer lobes 

 of maxillipeds roundish-oval, less than half length of inner lobes . . 



