338 



PART II. SYSTEMATIC ACCOUNT 



1 в§ 





: ш 



Fig. 135. Heptabrachia abyssicola: A - spermatophore (filament omitted); В -middle part of tube; 

 С -hind part of tube. (After Ivanov, 1952.) 



2. Heptabrachia gracilis Ivanov (Figs. 136-7) 



Ivanov, 1957a: 449, 461-5, 469, 493, 495-7, Figs. 31-4, 59; Dajoz, 1958: 236; Ivanov, 

 1960a: 1531, 1537, 1612, Fig. 1394; Ivanov, 1960c: 5, 12, 16, 20, 22, 96, 199, 200, 203-6, 

 211, 214, 215, 266, Figs. 87, 136-7. 



The fore-part of the body is cylindrical and the protosoma is only a 

 quarter the length of the mesosoma, from which it is divided by a clear 

 annular groove (Fig. 136^4, B), while the broad, more or less triangular 

 cephalic lobe is not divided from it at all. The very long tentacles, attached 

 in a horseshoe, number five to seven. Their pinnules have not been studied 

 because of the bad state of preservation of the material. A noteworthy feature 

 of the mesosoma is a transverse groove in front of the bridle, as a result of 

 which the front section of this segment looks like a broad girdle divided down 

 the mid-ventral line by a deep furrow (Fig. 136^4). Similar secondary meso- 

 somal grooves are found also in H. beringensis and in Polybrachia, which latter, 

 however, possesses not one but several mesosomal girdles (pp. 347 and 393). 

 The stout greyish, weakly cuticularized keels of the bridle, situated just a 



