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Show 11. A spid o siphon eleg an s Cliam. & Eysenli. Selenka,, tom. cit. p. 124. Loc. Pulau Bidan, Penang. Fifteen small specimens. 1 2 . A sp id o sipho n in su l a r is , sp. n o v . (Plate II. fig. 4 .) Loc. Pulau Bidan, Penang, Two damaged specimens. The longitudinal muscles are split into bundles which anastomose rather freely ; they appear stronger behind the level of the retractors, where they number about 22, but in front of this level the transverse bands appear more prominent and the longitudinal muscles number only 15. The retractor muscles are four in number, and take their origin a little behind the middle of the body, the ventrals arising from longitudinal muscles 2- 6, the dorsals from 5-6 only, a very little distance in front of the ventrals ; the pairs unite very quickly, but the united pairs do not join till moderately close to the tentacles. The nephridia are long, extending from their opening, at the same level as the anus, close to the base of the introvert, to some little distance behind the retractors ; they are brown in colour, and attached only in their front portion, which is slightly swollen. A well-marked spindle-muscle holds the intestine down to the hind end of the body, which, in the specimen figured, is invaginated for a little distance. Externally the body is a dirty-white and dotted with small brown papillae, which in the middle of the body are only visible under the lens, but which increase in size towards the hind end. The anal shield is circular, and formed of crowded, large, brown papillae. The introvert is less than half the length of the body ; in front it carries a few rows of hooks (fig. 4 b), and behind rather large papillae, each of which terminates in a dense, almost tooth-like structure (fig. 4 c). Along the dorsal line the papillae are enclosed by a dense brown pigment. E c h i u r i d a . Y I. Genus T h a l a s s em a . 13. T h a l a s s e m a s a b in u m , sp. nov. (Plate II. fig. 5.) Loc. Tale Sab, Singora. " In channel at top of brackish part." Five specimens. The characteristic features of this species are as follows :- a. The proboscis is short as compared with the body; b. There are two pairs of nephridia with spiral openings ; c. The muscle-sheath is continuous ; cl. The anal trees are short; which conjunction of characters at once separates it from the other members of the genus. The animal is small, measuring in 40 SIPUNCULIDS ETC. OF THE " SKEAt" EXPEDITION. [Jan. 17, |