LITUOLIDAE 103 



depths. It is probably related to the group of Trochammitia globigeriniformis, and is not 

 easily distinguished from small individuals of that species. 



Pearcey has recorded T. turbinota (Brady) from the Weddell Sea (P. 1914, SNA, 

 p. loii), but without an examination of his specimens it is not possible to determine 

 their identity. 



200. Trochammina tricamerata, sp.n. (Plate III, figs. 50-52). 

 Six stations: 175, 177; WS 482, 515, 517, 555. 



Test free, biconvex; on the dorsal side showing three convolutions each of rather 

 more than three chambers, slightly inflated, sutures somewhat depressed ; on the ventral 

 side showing only the last convolution of three very inflated chambers, with intervening 

 sutures deeply excavated. Aperture a small curved slit on inner edge of final chamber. 

 Wall thin, of rather coarse sand grains with much ferruginous cement, smooth but not 

 polished. Colour various shades of brown and yellow. 



Maximum breadth about 0-35 mm.; thickness up to 0-25 mm. 



Very rare, never more than two or three specimens at a station, the best at Sts. 175 

 and 177. The depths range between 50 and 3850 fathoms, but the latter depth at St. 

 WS 555 is exceptional, and only one small specimen was found there. It appears to be 

 confined to the Bransfield Strait and Bellingshausen Sea, and is probably related to 

 T. globiilosa (No. 198), diff"ering in its fewer chambers and lesser degree of inflation. 



201. Trochammina alternans, sp.n. (Plate III, fig. 24-27). 

 Five stations: 360; WS 203, 400, 468, 516. 



Test free, in outline like the figure eight, all chambers visible on the dorsal side, which 

 is convex, rising to the earliest chambers at the summit of a short spire. These earliest 

 chambers, four or five in number, are minute, dark in colour, and spirally arranged. 

 Subsequent chambers are added in pairs, opposite to each other ; they are inflated and 

 increase rapidly in size. On the ventral side only the last pair of chambers and a portion 

 of the ante-penultimate chamber are visible. Aperture an arched opening on the edge 

 of the final chamber. Constructed of fine sand and cement, thin- walled but firm. Colour 

 pale yellow except for the darker earliest chambers. 



Greatest breadth up to 0-4 mm. ; least breadth up to 0-3 mm. ; height about 0-2 mm. 

 Very rare at all stations, which are in the deep water of the Scotia and Bellingshausen 

 Seas, 261 1 -45 1 7 m. It is a very distinctive form allied to T. globulosa, but characterized 

 by its spiral having only two chambers to the convolution. 



202. Trochammina vesicularis. Goes (Plate III, figs. 44-46). 

 Trochammina vesicularis. Goes, 1894, ASF, p. 31, pi. vi, figs. 235-7. 



Three stations: 170, 360, 363. 



Common at St. 363, off Zavodovski Island in the South Sandwich group, depth 329- 

 278 m.; very rare at St. 360 in 3264 m. ; and a single specimen at St. 170, off Cape 

 Bowles, Clarence Island, 342 m. 



This elegant little species was described by Goes from 350 m. in the Spitzbergen Sea, 



