220 CEYLON PEARL OYSTER REPORT. 



certainly correct by the fact of their coming from the same locality. Under the 

 circumstances it seems desirable to give some details with regard to the species. 



There are two good specimens in the collection, one in spirit (R.N. 48) and one dry 

 (R. N. 99). The former (figured) is massive, irregular, attached by a broad spreading 

 base, from which compressed digitate or flabellate processes rise vertically upwards, 

 bearing small vents at their apices (vents about 1"5 millims. in diameter). The 

 surface is cactiform, with usually sharp-pointed but broad conuli, up to about 

 3 millims. in height, but usually less. The distance between the conuli varies 

 greatly, but they are usually widely separated from one another by intervals of about 

 8 millims. The surface between the conuli is smooth or wrinkled, finely granular, 

 under a lens very minutely reticulate and porous. The colour on the surface (in 

 spirit) is warm brown, internally it is much paler, yellowish. The texture is com- 

 pressible and resilient, but extraordinarily tough and leathery, so that it is very 

 difficult to cut sections. This leathery character is obviously due to the enormous 

 quantity of " filaments " which the sponge contains. Internally it is somewhat 

 cavernous, owing to the presence of numerous cylindrical canals running vertically 

 upwards towards the vents. This specimen measures about 190 millims. in greatest 

 breadth of base and 56 millims. in greatest height. 



The dry specimen is strongly compressed, flabellate, and only very slightly pro- 

 liferous, with a narrow margin bearing a row of vents. It contains much more sand 

 than the spirit specimen, but in other respects agrees closely. It measures about 

 135 millims. in height by 120 millims. in greatest breadth. 



The skeleton is composed principally of large sand-grains, with a comjxrratively 

 small quantity of spongin ; arranged as follows : ( 1 ) Very stout columns or tracts 

 of sand-grains run vertically through the sponge and end in the surface conuli. 

 These columns are compound structures, in which the sand-grains are held together 

 by numerous short, slender spongin threads running from one to the other, in much 

 the same way as Lendenfeld (66) has figured for Psammopemma marshalli. They 

 apparently represent an exaggerated condition of the trellis-like main fibres of certain 

 other Hircinise. (2) A very irregular network of more slender secondary fibres, 

 composed of sand-grains held together by spongin threads as in the main columns, 

 but the large sand-grains often only in single series. (3) In the dermal membrane 

 there is a thin layer of broken sponge-spicules and large sand-grains, the former lying 

 somewhat more superficially than the latter. Numerous broken spicules also occur 

 along with the sand in the deeper parts of the sponge. 



The canal-system appears to be that of a typical Hircinia, but, owing to the large 

 quantity of sand and :< filaments," it is impossible to get satisfactory sections. The 

 flagellate chambers are not well preserved, but they appear to be about 0'04 millim. 

 in diameter and approximately spherical, and the ground-substance between them is 

 finely granular. The soft tissues are very densely charged with filaments. These 

 have a maximum thickness of about 0'004 millim. between the heads. The heads, 



