1923] NATURAL SCIENCES OF PHILADELPHIA 215 



Sosanopsis armipotens sp. nov. Plate XV^llI, figs. 26-29. 



A single incomplete specimen of a slender and terete male worm 

 filled with sperm, reseml)ling Melinna, \nit lacking the post-branchial 

 membrane. 



Length 31 mm. of which the thorax is 11 mm.; maximum width 

 1.3 mm. The thorax consists of nineteen segments with setae 

 beginning on IV and continuing to XIX. About twenty abdominal 

 segments remain. 



As in Melinna the prostomium (Plate XVI II, figs. 26, 27) is simple 

 and truncate without any clearly defined characters and is coalesced 

 with the peristomium. No visible eyes. Below is a simple, horse- 

 shoe-shaped tentacular lobe bearing on each side a few* small terete 

 tentacles about as long as the prebranchial region and on each 

 side near the middle line a single enormous flattened tentacle 

 folded on itself longitudinally and dorsally, the dorso-lateral 

 margins of the groove marked with numerous fine transverse 

 ridges. When straightened and flattened these tentacles measure 

 12 mm. long and about 8 mm. wide, while the longest of the small 

 tentacles does not exceed 1 mm. 



Peristomium and II united (Plate XVIII, figs. 26, 27), together 

 forming a broad, simple truncate lower lip with a conspicuous oblong 

 yellow glandular area at its base. Somite III })ears below a stiff 

 glandular collar into which the head region maybe retracted ; laterally 

 it is continuous with the stiff lateral glandular walls l)ounding tlie 

 branchial area, but lacks distinct wings. Somites 1\' and \ , forming 

 the branchial region, are below and at the sides stiffened by a 

 thick layer of pale yellow glands. Ventral plates only two, one on 

 III, and one on IV and V united. At the sides the glandular areas 

 of these three segments coalesce and rise to the dorsal level as a 

 low ridge but not as a prominent wall as in many species of Melinna. 

 This ridge, which V)ounds the branchial area laterally slopes dor- 

 sally to VI and just b(4ow its edge bears the three short vertical 

 series of seta3 representing the parapodia of segments IV-\T. Xo 

 nuchal spines can be detected. 



The branchial area (Plate XVllI, fig. 26) occupying the dorsum of 

 segments IV to VI is narrow and bounded caudalh" 1 )y a narrow gland- 

 ular band across the dorsum of VII, which undoubtedly represents the 

 obsolete post-branchial fold. Four pairs of branchiae are borne 

 far forward on IV and are arranged as in Melinna, three behind 

 and one forward, all with their bases coalesced, the two outer 

 posterior most completely united and continued caudally by a 

 narrow ridge. All firmly attached, slender antl almost filiform, 

 the posterior subequal and the anterior more than one-thirtl 

 longer or nearly thr(>e times the width of the branchial region and 

 reaching to about segment XIV or XV. 



