HEPTABRACHIA TALBOTI 353 



The protosoma is separated from the mesosoma by a circular groove, 

 behind and over which the anterior mesosoma is drawn out into a collar-like 

 flap (Fig. B144v4, C). On the tentacular side* the collar is divided by a deep 

 groove which extends back, with a flap on each side, as far as the bridle. This 

 bridle is a ridge of thickened cuticle which encircles the mesosoma except for 

 a small gap on the tentacular side (Fig. B144v4, C). Behind the bridle the 

 mesosoma is smooth. Together the protosoma and mesosoma are 1-52 mm 

 long and the greatest width of either is 0-32 mm. The third, last, and longest 

 segment of the body is the metasoma, which in this specimen is 12 mm long 

 and certainly not complete. The first part (1-7 mm) is very much contracted 

 and twisted, and the closely packed papillae on the tentacular side (Fig. 

 B144v4) are probably normally arranged in two rows separated by a longi- 

 tudinal groove, as they are in many other pogonophores. The paired arrange- 

 ment of the papillae on this part of the body in other pogonophores has 

 earned it the name of the 'metameric' region. In the present specimen each 

 papilla is crowned with an oval adhesive plate with one thickened border 

 (Fig. B144y4, E). Behind the metameric region is a muscular region bearing a 

 few scattered papillae, with adhesive plates (in a mature specimen this is the 

 region which contains the gonads), extending for about 10 mm and ending 

 with two girdles of small toothed platelets (Fig. B144D). The specimen is 

 broken off at the second girdle and is also damaged at the level of the first, so 

 that the extent and shape of the girdles in the complete animal are not known. 

 Each girdle is made up of several irregular rows of platelets (Fig. B144-F, G), 

 of the shape and form found in many other pogonophores. The part of the 

 metasoma behind the girdles (postannular region) is missing; in other species 

 it is often as long as the preannular region. 



For a complete description it will be necessary to have a specimen with the 

 metasoma in good condition, in order to discover the true arrangement of the 

 papillae in all parts, and to clarify the arrangement of the girdles. Complete 

 tentacles are needed for measurement of their length and for investigation of 

 their pinnules, if present. 



However, with the material available, it is possible to place the species, 

 with reasonable certainty, in the genus Heptabrachia Ivanov 1952, and to 

 conclude that it is unlike any of the four species so far known. H. abyssicola, 

 H. gracilis, H. beringensis and H. subtilis were all described by Ivanov and he 

 has summarized their characteristics in a table (Ivanov, 1960, p. 214). 



* The tentacular side of the animal is ventral according to Ivanov (1955), dorsal according to 

 Jagersten (1956). 



