252 PART II. SYSTEMATIC ACCOUNT 



species. In two of these tubes animals were found, in one an almost mature 

 female, and in the other the front half of the body of a male. This species 

 has been named S. norvegicum. The more or less cylindrical fore-part of 

 the body is seven times as long as broad. The groove between the protosoma 

 and the mesosoma lies a little in front of the bridle. Ventrally it is distinct, 

 but on the dorsal side it becomes indiscernible or disappears altogether 

 (Fig. 126Д B). The strikingly large protosoma is three-quarters the length of 

 the mesosoma and, in the female, a little narrower than the mesosoma. The 

 small, conical, cephalic lobe is not divided from the rest of the protosoma, and 

 the long slender tentacle, free of pinnules, is attached not far from its tip. The 

 delicate, muddy-brown keels of the bridle, located on the front end of the 

 mesosoma, are fused together on the ventral side, where they are noticeably 

 thickened, but between their dorsal ends lies a considerable gap (Fig. YlbA, B, 

 C). The small portion of the mesosoma lying in front of the bridle has a nar- 

 row crack-like median ventral furrow. Behind the bridle is a well-developed 

 epidermal glandular girdle, widely interrupted on the dorsal side and only 

 narrowly continuous on the ventral side (Fig. 126C). A large part of the 

 mesosoma behind the glandular belt is occupied by two rows of internal 

 glands, which may be seen through the body-wall by transmitted light. The 

 boundary between the mesosoma and the metasoma is an annular groove, 

 only slightly arched backwards on the dorsal and ventral sides (Fig. \26A, B). 

 The rather long, metameric front part of the metasoma is only a little less 

 broad than the mesosoma, and the numerous small paired papillae are strongly 

 compressed together (Fig. \2ЬЛ). In each of the first few papillae one or two 

 pyriform glands are present. The ventral sulcus is narrow, and the dorsal 

 ciliated band begins immediately at the front edge of the trunk (Fig. 1265). 

 The nonmetameric part of the preannular region of the trunk is unknown. 

 There is no sharply defined zone of thickened papillae behind the genital 

 aperture in the female. The three girdles of toothed platelets lie on three 

 muscular thickenings of the trunk (Fig. 126Z)), and the first girdle is notice- 

 ably narrower than the others. The distance between it and the second girdle 

 is about one and a half times that between the second and third. The first and 

 second girdles are interrupted only on what appears to be the ventral side, but 

 the third girdle is interrupted both ventrally and dorsally. The toothed plate- 

 lets, arranged in 2-4 rows (Fig. 126£), are shaped like shoe-prints and each 

 possesses a well-developed front group of teeth, occupying about one-third 

 of the surface of the platelet. The anterior teeth are considerably smaller 

 than the posterior, and between the two groups runs a narrow but noticeable 

 interval clear of teeth (Fig. 126^). The platelets are 10-15/x long. 



