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Show 1905.] SIPUNCULIDS, ETC. OF THE " SKEAI'" EXPEDITION. 35 species, though it might possibly be referable to Th. pellucidum Fischer, which is, however, a Western form. The muscles number 12 or 13, but some of them are so indistinct as to make it impossible to be quite certain. The anal trees are quite short, brown, tapering, and simple. No other internal features can be made out. The proboscis is 10 mm. in length as compared with a body length of 40 mm., and in this agrees with Fischer's species (cf. Shipley, Willey's Zool. Res. part iii. p. 351). Each ventral hook has an accessory hook of about the same size lying close to it. 20. T h al a s sem a d e cam er on , sp. nov. (Plate I. fig. 5.) Loc. Chwaka, Zanzibar. I fab. In sand. One specimen. This species is characterised by the presence of four pairs of nephridia, which are, however, small in this individual and only slightly elongated. Two of them, moderately distant from each other, lie behind the sette ; and the other two, much closer together, in front of the set*. The body-wall is extremely thin; internally it is possible to distinguish ten, fairly broad, but inconspicuous, longitudinal muscles, which can also be seen from the outside shining through the skin. The anal trees are long, broad and brown at the base, but soon tapering and becoming transparent; simple and not dendritic in this individual. EX P L AN A T IO N OF PLATE f. Fig. 1. Physcosoma evisceratum (p. 31). a. Papilla from the front end of the body. b. Papilla from the hind end of the body. c. Hook. Fig. 2. Phascolosoma vnlgare, var. selenka (p. 31). a. Papilla from the introvert. b. Hook. Fig. 3. Phascolosoma glaucum (p. 32). a. Dissection showing internal anatomy. b. Papilla from the front end of the introvert. Fig. 4. Phascolosoma ivasini (p. 32). a. Dissection showing internal anatomy. b. Papillae from introvert. Fig. 5. Thalassema decameron (p. 35). a. Body laid open, to show nephridia, muscles, and anal trees, b. Skin from mid-body. G. On the Sipunculids and Echiurids collected during the " Skeat " Expedition to the Malay Peninsula. By W . F. L a n c h e s t e r , M .A , Assistant Lecturer and Demonstrator in Zoology in University College, Dundee *. [Received November 1, 1901.] (Plate I l .f) This collection, which Mr. Shipley kindly put into my hands for determination, contains 12 species of Sipunculids and 1 of Echiurids ; the latter is a new form, as are also four of the * Communicated b y th e S e c r e t a r y . f For explanation of the Plate, see p. 41. |
