HEPTABRACHIA ABYSSICOLA 337 



very long postannular region of the trunk has on its ventral side about 40 

 transverse metameric rows, each of 7-8, of small papillae, arranged rather 

 regularly at more or less equal intervals (Fig. 1347). The transverse cuticular 

 plaques, 35-40/x long, on the papillae are rod-shaped and curved just a little 

 forward (Fig. 134/). 



Measurements made on two individuals gave the following results: 

 length of the fore-part of the body, 1-1-1 -7 mm; breadth of the mesosoma, 

 0-23-0-25 mm; overall length, excluding the tentacle, 59-7-71-1 mm; ratio 

 of length of whole body to its breadth, c. 270:1. The preannular region of 

 the trunk is one and a half times as long as the postannular section, and the 

 metameric part accounts for only a fifteenth of the whole length of the trunk. 



The spermatophores are shaped like flat leaves, drawn out into a long 

 point at one end and rounded at the other (Fig. 135^4). The transparent 

 membrane of the spermatophore is very thin and delicate and inside it lie 

 the numerous thread-like sperm with the head ends towards the rounded 

 end of the spermatophore and fanning out to lie perpendicular to the wall in 

 this part. A cortical zone at the broad end of the spermatophore is free of 

 sperm. The filament which one would expect to find attached to this end 

 has not been observed (Ivanov, 1952), but there is little doubt of its existence, 

 the more so as it has been described in H. gracilis (Ivanov, 1957a). The 

 spermatophores are 0-34 mm long. 



The anterior part of the slender semi-transparent light-brown tube has 

 irregular brown rings (Fig. 1355), and farther back they become longer and 

 diffuse (Fig. 135C). The longest fragment measured 122 mm, but the total 

 length of the tube must be not less than 200 mm, with a diameter of 0-33 mm. 



Like H. subtilis, H. abyssicola has no secondary grooves on the mesosoma 

 in front of the bridle, but it is distinguished by the large cuticular plaques (a 

 feature not encountered in other species) and by the unfused keels of the bridle. 



Material : 4 specimens in broken tubes. 



Locality: the Kuril-Kamchatka Trench. Depth: 6475-8164 m. 



Fig. 134. Heptabrachia abyssicola: A - front end of a female from the ventral, and, В -from the 

 dorsal side ; С - region of thickened papillae from the ventral side ; D - cuticular plaque from the 

 front part of the metasoma ; E - region of the girdles from the ventral, and, F - from the dorsal 

 side; G - part of a girdle; H - toothed platelet; /-part of the postannular region from the ventral 

 side ; Jf - hoop-shaped plaques from the postannular region. 



an - girdles ; с - cephalic lobe ; со - dorsal ciliated band ; da - anterior group of teeth ; dp - hind 

 group of teeth; /-keel of the bridle; tns - mesosoma ; mts - metasoma; p- cuticular plaque; 

 pa - metameric papillae ; pa 1 - papillae of the zone of thickening ; pa 2 - ventral papilla behind the 

 girdles ; pa 3 - papillae of the postannular region ; ps - protosoma ; s 1 - groove between the proto- 

 soma and the mesosoma ; s 2 - groove between the mesosoma and the metasoma ; sv - ventral sulcus ; 

 tc - tentacular crown ; vv - ventral blood vessel seen by transparency. 



