42 THE VOYAGE OF H.M.S. CHALLENGER. 



Sponge massive, lumpy, forming irregular, roundish, club-shaped or turbinate 

 masses, which are composed almost entirely of calcareous Globigerina shells, cemented 

 together by a scarce maltha. No symbiotic Spongoxenia. 



Psammopemma calcareum sometimes assumes, like the preceding species, the 

 characteristic subregular turbinate form, which is figured in PI. VII. fig. 5, taken from 

 Station 89 ; the same form has been described in Holopsamma turbo by Carter in 1885, 1 

 but the central depression of the summit of the funnel-shaped body has not the large 

 vent or osculum in its centre, as described in the latter species. The whole surface is 

 coarsely porous, pierced by innumerable smaller and larger pores, but no distinct oscula are 

 visible ; they are absent also in the typical species of the genus first described by Marshall. 

 The dry body of our Psammopemma calcareum is white, hard, chalk-like, friable, 

 composed almost entirely of smaller and larger Globigerina shells, which are cemented 

 together by a scanty clear maltha. After dissolving the calcareous matter in hydro- 

 chloric acid, there remains a small residuum, composed mainly of branched canals, 

 similar to those of Holopsamma cretaceum (PI. VII. fig. 7C). The membrana propria 

 of the canal-wall is reinforced by small xenophya (sand- grains). The diameter of the 

 specimen figured is between 20 and 25 mm. 



Similar pieces of a chalk-like Psammina of the same composition occur also at other 

 Challenger stations, where the bottom of the sea is covered with Globigerina ooze, 

 but they have not that regular turbinate form, seen only in the single specimen figured 

 from Station 89. The pieces, which were occasionally observed in the Globigerina ooze 

 of Stations 220, 270, &c, were for the most part roundish or club-shaped, 2 to 8 mm., 

 rarely 12 to 20 mm., in diameter. 



Family III. Spongelidji, Lendenfeld (Pis. IV.-VL). 



Definition. — Keratosa with a reticular horny skeleton, composed of anastomosing 

 spongin-fibres, which enclose xenophya (or manifold foreign bodies). Maltha 

 transparent, not granular, also often supported by xenophya. Canal-system vesicular, 

 developed on the Leuconal-type (similar to Spongelia). 



The family Spongelidaa (Lendenfeld) or Dysideidse (Marshall) comprises those 

 Keratosa which produce a network of anastomosing homogenous spongin-fibres and 

 possess a clear maltha, or a transparent, not granular, ground-mass of the mesoderm. 

 They differ in this latter character from the closely-albed Euspongidee (the Spongidae of 

 Vosmaer), which all possess a granular maltha (like the Aplysinidse). Most of the 

 Spongelidee — especially all the deep-sea forms — are arenaceous sponges or " Psammo- 

 spongiae," and possess a pseudo-skeleton composed of manifold xenophya or foreign bodies 

 (sand-grains, calcareous shells of Foraminifera, siliceous shells of Radiolaria and Diatoms, 



1 Loc. tit., p. 213. 



