330 DISCOVERY REPORTS 



W. depressa is readily distinguished from W. hemisphaerica by (i) its low convexity, 

 (2) its irregular contour, and (3) by the invariable absence of ferruginous cement. The 

 minute sand grains, though firmly agglomerated, are not cemented together, and the test 

 can be opened with a needle point without fracture, an impossibility with the firmly 

 cemented hemisphere of W. hemisphaerica. 



Genus Tholosina, Rhumbler, 1895 



65. Tholosina bulla (Brady). 



Placopsilina bulla, Brady, 1879, etc., RRC, 1881, p. 51 ; 1884, FC, p. 315, pi. xxxv, figs. 16, 17. 

 Tholosina bulla, Cushman, 1910, etc., FNP, 1910, p. 49, fig. 55. 



Five stations: WS 213, 215, 225, 246, 433. 



The semi-globular type of Brady is a deep-water organism, as evidenced by the shape 

 of the test. No very typical examples occur, the best being at WS 246. 



66. Tholosina protea, sp.n. (Plate VIII, figs. 5-8). 

 Five stations: WS 94, 213, 225, 243, 246. 



Test normally adherent, sometimes becoming detached and assuming the free con- 

 dition, consisting of a single thick-walled chamber composed of very fine sand and mud 

 firmly agglutinated with cement ; surface usually smooth but not polished ; aperture one 

 or more small holes situated at the extremities; shape protean, dependent upon the 

 nature of the surface of attachment. Colour varying from snowy white, which is not 

 uncommon, to nearly black, according to the material employed. Dimensions very 

 variable, ranging up to 2-0 mm., but on an average about i-o mm. in greatest diameter. 



We have given this name to an organism with which we have long been familiar in 

 dredged material from our own coasts. The Falklands specimens show little difference 

 except in their greater size and abundance. 



It may be regarded as the shallow- water equivalent of the deep sea T. bulla. In 

 shape it is truly protean, the form of the " house " being governed by the contour of the 

 surface on which it is built. On flat surfaces it is semi-globular, sometimes nearly 

 globular, with difficulty separable from T. bulla. When attached to the stalk of a zoophyte 

 its length may be many times its breadth, and separate individuals are sometimes so 

 closely situated as to give the impression of a multilocular organism. It is possible that 

 the doubtful organism Placopsilina kiiigsleyi, Siddall (S. 1886, LMBC, p. 54, pi. i, fig. i) 

 may have been such a double specimen. The description and figure are poor, and the 

 Type is missing from the Siddall collection now in our possession. A favourite position 

 is in the forking angle of a branching zoophyte, where it becomes attached to both 

 branches and forms a wedge-shaped and irregular "house". It sometimes surrounds 

 a slender branch. Finally, it may become detached and continue a free existence as a 

 more or less rounded object, usually showing traces of its original point of attachment. 



It is probably abundant where conditions are favourable. Not much of our material 

 was of a suitable nature, but it was common and varied at WS 243. 



