HEPTABRACHIA CTENOPHORA 359 



thickened anterior rim crossed by thin streaks perpendicular to the edge. 

 Their greatest diameter varies from 30 to 40/x (Fig. F144.E). On the papillae 

 of the zone of thickening the plaques are much the same size, except that they 

 are more expanded from side to side (Fig. F144/ r ). 



The two girdles, looking like thick transverse ridges, lie close together. 

 Both have a wide gap on the ventral side and the posterior is broken dorsally 

 also (Fig. F144G, H). The front girdle dips backwards in an arch on the 

 dorsal side. Several small ventral papillae with cuticular plaques are found 

 in the region of the girdles. The yellowish toothed platelets of the girdles 

 form two or three rows (Fig. F1447). They are very like those of H. gracilis 

 and each bears a small group of teeth pointing backwards on the narrower 

 front end (Fig. F144/). The platelets are 11-18/* long. 



The postannular region of the trunk is long and slender. The transverse 

 rows of ventral papillae lie on metameric dermal ridges situated at rather 

 frequent intervals (Fig. F144AT). The cuticular plaques here, in contra- 

 distinction to those of other species of Heptabrachia, are not rod-shaped but 

 oval (Fig. F144L). Their greatest diameter varies from 20 to 50^. 



This description is based on a single individual, a female, whose dimen- 

 sions are as follows (mm) : 



Length of the tentacles 17-5 



Length of the fore-part of the body 2-8 



Breadth of the mesosoma 0-5 



Length of the preannular region of the trunk 71-6 



Length of the postannular region of the trunk more than 25 



Overall length of the body, including the tentacles c. 120 



The dark brown lustrous ringed but unsegmented tube is rather coarse 



and stiff in the middle region. Its anterior part (not less than 20 mm long) is 



membranous and transparent and the walls collapse easily. The rings appear 



very gradually; at first they are hardly noticeable, pale brown with hazy 



uneven outlines and incomplete (Fig. G144y4); then, more caudally, they 



become brown or dark brown and their edges more even, but frequently 



here, as farther forward, one encounters irregularities — fusion of adjacent 



rings or underdevelopment of individual rings. Anteriorly the rings are a 



fifth or a quarter as long as the tube is wide, in the middle part of the 



tube a quarter or a third. The clear interspaces between the rings are rather 



broad. The hind third of the tube has more or less regular coarse dark 



brown rings each with a darker posterior border (Fig. G144.5). Their 



length here is a half to a third the diameter of the tube. The clear 



interspaces between the rings are here very narrow, in places almost 



