TUNIC AT A. 333 



more delicate atrial tentacles (fig. 18) which have not been previously noticed. 

 Fig. 13 shows the alimentary canal and fig. 15 the gonads. 



In examining a very simple Polystyelid such as this, with no folds in the branchial 

 sac, one cannot but be struck with the resemblance not merely to the Styelidae and 

 to the Botryllidse, which has often been insisted upon, but also to such Clavelinidre 

 as the genus Ecteinascidia. The fact is, that the Polystyelids are an annectant 

 group, and such simple forms as Diandrocarpa lead on from the more advanced 

 Clavelinids (such as Sluiter's Ecteinascidia nexa) to the Botryllids and the Styelids. 



Family : P.OTEYLLID^E. 

 Botryllus ater, n. sp. Plate VII. , figs. 19 and 20. 



Colony a small irregular, encrusting patch from the oyster cages on the Cheval 

 Paar. 



Test clear and transparent, crowded with terminal knobs in its marginal part. 



Ascidiozooids small, and especially narrow ; pigmented very darkly and having the 

 branchial aperture so black that it appears to the eye as a distinct dot upon the outer 

 end of the ascidiozooid. From five to ten ascidiozooids in a system. 



Mantle and Branchial Sac densely crowded with dark pigment. 



Botrylloides chevalense, n. sp. Plate VII., figs. 21 to 24. 



Colony thin and encrusting, of irregular form ; six colonies range from 3 centims. x 

 1 centim. to 5 centims. x 3 centims. ; of a red colour (in formol), varying from pale 

 brick red to purple. 



Ascidiozooids, measuring 1'5 millims, x 1 millim., arranged in elliptical or linear, 

 rarely branching systems (fig. 21). 



Branchial Sac richly pigmented, and having about 10 rows of stigmata (fig. 23). 



Test clear and transparent, but having a large number of terminal knobs of vessels 

 in its marginal part (fig. 22). 



Tentacles of two sizes (fig. 24), four larger and four smaller. 



Locality : Attached to pearl oysters from the oyster cages suspended from the 

 ship while on the Cheval Paar. 



Botrylloides nigrum, n. sp. Plate VII., fig. 25. 



Colony small smooth glossy black patches encrusting the branches of Colella 

 arenosa. Systems forming a net-work of branching lines (fig. 25). 

 Test very tough on surface, deeply pigmented. 

 Mantle with longitudinal muscles only. 

 Branchial Sac with many rows of stigmata. 

 Locality : South of Modragam Paar, 6 fathoms. 



