REPORT ON THE DEEP-SEA KERATOSA. 41 



only a thin envelope around the enclosed foreign bodies." I was not able to discover 

 any trace of true spongin in the different species of Psammop&mma now described. 



This genus seems to be widely distributed in the deep sea, but has been overlooked 

 hitherto, owing to its insignificant shape and usually small size. I have found small 

 fragments belonging to Psammopemma in several soundings ; they are like irregular lumps 

 or crusts, composed of the sediment covering the sea-bottom. But a closer examination 

 informs us that the apparent sandy concrement is traversed by a branched canal-system, 

 in the course of which are interpolated numerous flagellated chambers. 



Psammopemma radiolarium, n. sp. (PI. VII. figs. 4A, 4B). 



Habitat. — Tropical Pacific, Station 272; September 8, 1875 ; lat. 3° 48' S., long. 

 152° 56' W.; depth, 2600 fathoms; bottom, Eadiolarian ooze. 



Sponge lumpy, forming irregular, roundish, clavate or turbinate masses, which are 

 composed almost entirely of siliceous Radiolarian tests, cemented together by a scarce 

 maltha. No symbiotic Spongoxenia. 



Psammopemma radiolarium, in the characteristic turbinate form, which is represented 

 in PI. VII. fig. 4A from the side, fig. 4B from below, was found at Station 272 ; similar 

 specimens occur also in the soundings of Stations 270, 271, and 274, usually in the form of 

 irregular, roundish or cake-shaped, massive lumps, which at first sight were regarded as 

 mere inorganic concrements of Radiolarian ooze. A closer examination, however, 

 principally by means of different sections stained by carmine, informed me that the 

 whole sandy mass of these apparently homogeneous lumps is traversed by an irregularly 

 branched canal-system, opening on the surface by innumerable fine pores. No flagello- 

 chambers nor oscula were visible, but comparison with the similar lumps of 

 the following species makes it very probable that it belongs to this genus. The porous 

 lumps had partly the form of a flat cake or a subglobose mass, partly of a pedunculate 

 club or an inverted cone, sometimes like a peg-top. The diameter of the dry lumps is 

 from 5 to 20 mm. The consistence is that of a soft sandstone or of a friable marl, the 

 colour light grey or whitish. The xenophya of this species are exclusively Radiolarian 

 tests, cemented together by a very scanty maltha ; sometimes a few fragments of 

 siliceous sponge spicules are intermingled. 



Psammopemma calcareum, n. sp. (PI. VII. fig. 5). 



Habitat. — Tropical Atlantic, between the Canary and Cape Verde Islands, Station 

 89; July 23, 1873; lat. 22° 18' N., long. 22° 2' W.; depth, 2400 fathoms ; bottom, 

 Globigerina ooze. 



(ZOOL. CHALL. ESP. — PART LXXXII. — 1889. Nnnil 6 



