348 PART II. SYSTEMATIC ACCOUNT 



narrow, mid-ventral furrow (Fig. 143 A). The pale, narrow keels of the bridle 

 are fused neither ventrally nor dorsally, while the ridges on which they lie 

 are but weakly developed (Fig. 143/4, B). The strongly bevelled hind edge of 

 the mesosoma is notched in the mid-ventral line (Fig. 143.4). 



The anterior metameric part of the trunk is short (Fig. 142), and the com- 

 paratively small, rounded papillae along the sides of the narrow ventral 

 sulcus (Fig. 143/4) number 24-26 pairs. Towards the hind end of the meta- 

 meric section they grow larger and come to occupy a lateral situation so that 

 the trunk widens here and the ventral sulcus opens out. The oval cuticular 

 plaques have dark crescentic thickenings along their front edges and measure 

 25/л across (Fig. 144.4). The dorsal ciliated band is well developed along the 

 whole length of the metameric part (Fig. 1435). The succeeding very long, 

 non-metameric part of the trunk bears scattered rounded papillae, mainly 

 on the ventral side (Fig. 142). In both specimens the zone of thickened 

 papillae is formed of eleven large ventral papillae crowded together in dis- 

 order (Fig. 143 C), each of which has an oval cuticular plaque 32-35/* across 

 (Fig. 1445). Two girdles of the usual appearance lie on well-defined ridges. 

 The first girdle is interrupted both dorsally and ventrally, the second only 

 on the ventral side (Fig. 143 Д E). Between the ventral ends of each girdle is 

 a single rounded papilla with a plaque, while behind the girdles lies a large 

 spherical papilla with no plaque (Fig. 143£). The biserial toothed platelets 

 (Fig. 143P) narrow a little towards the front end. Each is furnished with a 

 small but well-developed anterior group of teeth, and measures 11-13-5/x 

 long. The very long postannular region of the metasoma is noticeably 

 broader than the preannular section (Fig. 142), and bears on its ventral side 

 up to 36 transverse metameric rows of adhesive papillae, each row consisting 

 of 4-6 papillae (Fig. 143Я). The latter are rounded and crowded together, 

 and each bears a rod-shaped plaque 35-45/a long (Fig. 144C). 



The various parts of the body have the following dimensions : length of 

 tentacular crown, 5 mm; length of the fore-part of the body, 1-5-1-8 mm; 



Fig. 143. Heptabrachia beringensis: A - front end of a female from the ventral, and, В - from the 

 dorsal side ; С - zone of thickened papillae from the ventral side ; D - region of the girdles in 

 dorsal, and, E - in ventral view; F - part of a girdle; G - toothed platelet from one side; //-part 

 of the postannular region in ventral view. 



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

 group of teeth;/- keel of the bridle; ms - mesosoma; mts - metasoma; p - cuticular plaques; 

 pa - metameric papillae ;ра г - papillae of the zone of thickening ; pa 2 - ventral papilla, lying behind 

 the girdles; pa 3 - postannular papillae; ps - protosoma; s 1 - groove between protosoma and the 

 mesosoma; j 2 - groove between the mesosoma and the metasoma; sv - ventral sulcus; tc - ten- 

 tacular crown ; vv - ventral blood vessel seen by transparency. 



