334 CEYLON PEARL OYSTER REPORT. 



Family : OISTOMID.E. 

 Colella arenosa, n. sp. Plate VII., figs. 26 to 29. 



Colony consisting of branched masses (fig. 27) growing through sponges and other 

 attached organisms, and partly encrusted with the black Botryttoides niger. The 

 base and larger branches are thickly covered with attached and embedded sand. 

 The twigs terminate in rounded knobs of a pale violet colour and nearly free from 

 sand (fig. 26). Some of the larger masses measure 6 centims. x 3 centime, over all ; 

 the branches are 2 millims. to 3 millims. in diameter ; the knobs are about 4 nnllims. 

 across the free end. 



Ascidiozooids placed in the free ends of the knobs, from 12 to 20 in each, and 

 having the usual structure of the genus (fig. 26). 



The violet pigmentation of the test in these specimens is found, even in the 

 branches, under the sandy coating. 



Locality : South of Modragam Paar, 6 fathoms ; half a dozen colonies and frag- 

 ments. There are also three colonies from Station LXIX., Chilaw Paar, 8 to 11 

 fathoms, which have exactly the appearance and structure of the above except that 

 the violet pigment is absent, and the free ends of the knobs are dark grey. 



Cystodytes ceylonensis, n. sp. Plate VIII. , figs. 23 to 25. 



About a dozen small, rounded, or lobed (fig. 23), encrusting colonies belonging to 

 the genus Cystodytes were obtained from Talaivillu Paar, 8 fathoms. They were of 

 a bright red purple colour when alive, and range in size from 1 centim. across to 

 2 centims. x 1*5 centims. The thickness from the attached to the free surface is 

 5 millims. The colour now, after preservation in alcohol, is a dark greyish brown, 

 and the ascidiozooids show through indistinctly as dirty yellow streaks. Each 

 ascidiozooid has the usual thick calcareous envelope (fig. 24), and the component discs 

 are marked with delicate radial stria? (fig. 25). 



A group of several little similar brown colonies, which are indistinguishable from 

 the above in the preserved condition, were dredged at the south-east end of Ceylon 

 on February 13. The colour when alive was not noted. 



In structure this form closely resembles Cystodytes philippinensis, Hrdn., obtained 

 by the "Challenger" expedition, but differs in colour and in having the discs 

 relatively thinner and more finely striated. 



Family: POLYCLINIDiE. 



? Polyclinum nigrum, Hrdn. 



A large black colony and some smaller pieces from the pearl banks, Gulf of Manaar, 

 measuring about 6 centims. x 6 centims. and extending up to 1'5 centims. in thick- 

 ness, may be this Australian species. Our colony has a very smooth shining black 

 surface, and occurs growing over masses of sponges, &c. The surface is marked by 



