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Show 34 OX THE GEPIIYREAX WORMS OF ZAXZIBAR, ETC'. [Jan. 17, 16. Aspidosiphox TRUXCATUS, Kef. Selenka, tom. cit. p. 118 (1883); Sluiter, Siboga-Exp. p. 17 (1902). Loc. Wasin, British East Africa ; 10 fathoms. One very small specimen. E c h i u r i d a . VI. Genus T h a l a s s em a . 17. T h al a s sem a b a r o n i i Greeff. Greeff, Die Echiuren, Nov. Act. Acarl. N. Cur. xli. p. 151, pi. vi. fig. 64 (1879). Loc. Zanzibar Channel. Hah. Shore, above lowest tide-level. The anal trees appear simple and not dendritic in this single specimen, as they do also in at least two among those collected by Dr. Willey. This character, together with the lack of any traces of the nephridia (which I cannot find either in this or in one of Dr. Willey's specimens), I take to be due to the fact that the individuals in question may be young. There is also a small globular diverticulum on the dorsal side of the rectum in this species. Mr. Crossland has a note on the colour of this specimen to the following effect : " Crimson-lake colour, with light-green proboscis." Previous descriptions of the colours in this species give them as being dark-green in the body with violet stripes. Evidently, then, the colour-character is not necessarily constant, for, despite the absence of nephridia, I feel no doubt as to the correctness of my diagnosis on anatomical grounds, especially after comparing them with the specimens from Dr. Willey's collection. 18. T h a l a s sem a m o e b ii Greeff. Greeff, tom. cit. p. 152. Loc. Chwaka Bay. Kokotoni Bay. Hab. In sand in sheltered bays like the above. Two specimens, on which Mr. Crossland has the accompanying note :- " Abundant in sheltered bays in sand above low-tide level, but extremely difficult to secure, as the burrows extend into crevices in the rocks below the sand. The larger specimens I never succeeded in obtaining. They occur with proboscides a foot or more long " (this presumably refers to those of large size) " when lying extended on the sand. Colour pink, owing to crelomic fluid seen through skin. Proboscis cream-coloured and more opaque." 19. T h al a s sem a sp. ? Loc. Chwaka, Zanzibar. A single specimen in a very bad state of preservation. It is impossible to refer this specimen with any certainty to any known |