1905.] GEPHYREAN ^YORMS OF ZANZIBAR, ETC, 29 



16 being Sipunculids and 4 Echiurids. Of the Sipunculids three, 

 and of the Echiurids one, are new ; the latter, a Thalassema, 

 presents the novel feature of foiu* pairs of nephridia, the greatest 

 number hitherto met with in that genus. Unfoi'tunately the 

 Echiurids are not at all well preserved, and it is evident that the 

 preservation of these animals needs even moi-e careful attention 

 than in the case of the Sipunculids. In this group, moreover, 

 I notice that, whether due to contraction or otherwise, the 

 nephridia and anal trees are apt to lose their characteristic 

 appearance, the nephridia appearing small or even absent, and 

 the anal trees simple in a species in which they are really 

 dendritic. 



SiPUNCULIDA. 



I. Genus SiPUNCULus. 



1. SiPUNCULus iNDicus Peters. 



Arch. f. Anat. u. Phys. p. 382 (1850). 



Log. Pemba Island. 



Hcd). From the eastern I'eefs in sand near the shore. 



Two large specimens, the internal organs of which are not 

 sufficiently well preserved to enable me to add anything to our 

 knowledge of their general anatomy. 



2. SiPUNCULus EDULis Lamarck. 



Sluiter, Natuurk. Tijds. Nederl. Ind. xlv. p. 484 (1886). 



Loc. Chwaka Bay, Zanzibar. 

 Eab. Shore at low tide. 



Several examples ; in one of which the transverse dissepiments 

 are absent. 



3. SiPUNCULus CUMANENSIS Kef. 



Selenka, Die Sipunciiliden (Semper's Reisen, iv. p. 104). 

 Loc. Chwaka Bay, Zanzibar. 



Three specimens corresponding with Grube's var. semiritgosics. 

 Log, Zanzibar. 

 Two specimens of var. vitreus. 



4. SiPUNCULus TITUBANS Sel. & BUlow, 



Selenka, torn. cit. p. 57. 



Loc. Chwaka Bay, Zanzibar ; two large specimens. 



This is a very clearly defined species, and these specimens 

 agree closely with the description. The only comment I have 

 to make on the original account is that, so far at least as concerns 

 these examples, the papillae on the introvert, though certainly 

 " von dreieckiger Form," are not so obviously so as in the case of 

 S. indicus : the angles are rather softened down. This character 

 together with the relative positions of the nephridial and anal 



