336 CEYLON PEARL OYSTER REPORT. 



Test with a few sand-grains scattered on the surface and others embedded in the 

 superficial layers (fig. 2) : numerous pigment cells present which give the orange 

 colour to the colony (figs. 3 and 4). 



Mantle with strong muscle bundles running both longitudinally and transversely, 

 and causing considerable corrugation of the thorax (fig. 5). 



Alimentary Canal forming a large loop, stomach with longitudinal folds, rectum 

 wide (fig. 6). 



Locality : Cheval Paar, 7 fathoms, one colony. 



There are two other colonies in the collection from the Gulf of Manaar which, 

 notwithstanding their rather different appearance, I am inclined to refer also to this 

 species. The one is a grey Psammaplidium measuring 7 centims. x 5 centims. x 1^ 

 centims., rounded, smooth, and only slightly sandy. The test is grey and transparent, 

 allowing the more opaque grey ascidiozooids to show through, and only differing from 

 the test of Ps. aurantiacum, as described above, in the absence of pigment cells. 



The other colony is a hemispherical mass, 4 centims. x 4 centims. x 2 centims., of 

 grey colour, but not so transparent as the last and having a yellowish tint. The 

 thorax, abdomen and post-abdomen are each about 1 millim. in length ; there are 

 eight large tentacles ; the stigmata are small and of rounded form. 



Psammaplidium, spp., A and B (? n. spp.) PL VIII., fig. 7 : PL IX., figs. 10, 11. 



In addition to the two species of Psammaplidium described above, there are two 

 others which may possibly be distinct from all known species, and from one another, 

 but which I do not feel sufficiently certain of to describe from the present specimens. 

 Both species are densely sandy, and of both one or two large colonies were found in 

 addition to fragments. 



The first form (A) is a plano-convex mass, the largest colony measuring 9 centims. 

 x 6 centims. x 3 centims., and probably attached by the whole of the flat surface. 

 The upper rounded surface is divided up into many lobes (Plate IX., fig. 10) which, 

 however, are closely packed together. The mass is most closely impregnated with 

 sand, both on the surface and throughout its depths, so as to appear on section like 

 a consolidated mass of sand. The ascidiozooids are small, not at all abundant, and 

 can only be separated in fragments. They show nothing unusual or specially 

 characteristic in their structure. This colony was dredged in the Gulf of Mauaar in 

 February, 1902 ; and a second, measuring 6 centims. x 5 centims. x 2^ centims., is 

 from Station LIIL, 10 miles north of Cheval Paar, 10 fathoms. 



The second colony (B) measures 7 centims. x 4 centims. x 3 centims., and is 

 irregularly lobed and produced into bars which join, leaving holes. The surface is 

 covered with a reddish sand, formed of very fine and uniform grains of ellipsoidal 

 shape and quite smooth, which surround the anterior ends of the ascidiozooids 

 (Plate VIII., fig. 7). In addition to these uniform red granules, which are singularly 

 like fajcal pellets, there are a few ordinary irregular sand-grains embedded in the test. 



1 



