20 



3. Species inhabiting depths from 200-500 m to 2,000-3,000 m, 

 i.e., dwellers of the meso- and bathypelagic. Some inhabit only the 

 bathypelagic layer, almost never rising to depths less than 500 m ' T 

 (such species are marked with an asterisk). Others, contrarily, especially 

 in the juvenile stage and in warm-water regions, rise even to the 

 near-surface layers. This group includes the majority of Physosomata 

 species: Lanceola serrata, Scypholanceola aestiva", Prolanceola 

 vibiliformis, Mimonecteola beebei, M. diomedeae, Microphasma agassizi, 

 Microphasmoides vitjazi, Mimonectes gaussi, M. loveni, M. sphaericus, 

 Scina curvidactyla, S. wolterecki, S. borealis, S. spinosa, S. indica, 

 S. submarginata, S. typhlops*, S. pusilla, S. wagleri* , and Ctenoscina 

 brevicaudata. 



4. Eurybathic species inhabiting a wide range of depths from 

 200-500 (1,000) m to 5,000-6000 m, and possibly, even deeper. These 

 are: Lanceola sayana, L. pacifica, L. loveni, L. clausi, Chuneola major, 

 and Scina rattrayi keilhacki. 



5. Species of still deeper waters inhabiting the abyssopelagic: 

 adults are generally not found above 2,000-3,000 m. The lower limit 

 of their distribution often is not clear. Some of these species are 

 found only at a depth of 4,000-5,000 m, while others have been 

 found in catches from depths of 5,000-6,000 m and 6,000-7,000 m 

 (marked with an asterisk). This group includes: Lanceola laticarpa, 

 L. clausi gracilis*, L. sphaerica* , L. chelifera, Scypholanceola agassizi, 

 Metalanceola chevreuxi, Mimoscina gracilipes, Scina wagleri abyssalis*, 

 Ctenoscina macrocarpa, and Spinoscina spinosa. Hyperiideans have not 

 been reported to date at depths greater than 7,000 m. Species inhabiting 

 only the ultra-abyssal zone are absent. 



The change in hyperiidean fauna with depth becomes very clear if 

 we compare the number of species found at different depths, and how 

 27 many species are found in each depth interval of the upper boundary of 

 distribution. Such a comparison is presented in Tables 1 and 2. Natu- 

 rally, it does not entail the entire fauna but only those species for which 

 information was available on the range of vertical distribution. 



It can be seen from Table 1 that the Physosomata fauna from the 

 meso- and bathypelagic is the richest. In the cold-water Kuril' sk region 

 the largest number of species (nearly 40% of that part of the fauna exam- 

 ined) has an upper boundary of distribution in the upper part of the tran- 

 sitional layer at depths of 200-500 m. In the more uniform 750-1,000 m 

 layer additional species do not occur at all. In the 1,000-1,500 m layer 

 again several species appear which do not rise to lesser depths. From 

 1,500 to 2,500 m the faunal composition does not change, while at 



Tt Changed from "1,000 m" in Russian text by authors. — ^Ed. 



