ROTALIINAE 413 



341. Discorbis millettii (Wright). 



Discorbina millettii, Wright, 1910-11, ECM, p. 13, pi. ii, figs. 14-17. 

 Discorbina millettii, Heron-Allen and Earland, 1913, CI, p. 121, pi. x, figs. 5-7. 



Four stations: 48; WS 84, 87, 88. 



Never occurring in any numbers, but excellent specimens at WS 87 and 88. 



342. Discorbis plana, sp.n. (Plate XIV, figs. 9-12). 

 Four stations: 388; WS 71, 87, 88. 



Test nearly circular, highly polished, plano-convex, much compressed; peripheral 

 margin sub-acute, but not carinate ; superior surface exhibiting about three convolutions, 

 4-5 chambers in each, increasing somewhat rapidly in size, sutural lines recurved and 

 flush but distinct; inferior surface depressed towards the umbilicus, exhibiting the 

 chambers of the last convolution only, sutural lines somewhat depressed ; the interior 

 margins of the chambers on this side are rather plicated, and sometimes have a few 

 beads in the umbilicus ; aperture, a slit on the inner edge of the last chamber. Colour 

 yellowish when young, becoming glassy white. 



The size is very variable, large specimens range up to breadth, 0-50 mm.; height, 

 o-io mm. 



Not uncommon at 388 and WS 88, rarer at the other stations. 



This is rather a striking species, and not very near any of the other local forms. It is 

 perhaps most closely related to D. nitida and D. millettii, but cannot be confused with 

 them. A specimen "budding" was found at WS 88 (fig. 12) and a sessile specimen at 

 WS87. 



343. Discorbis orbicularis (Terquem). 



Rosalina orbicularis, Terquem, 1875, etc., APD, 1876, p. 75, pi. ix, fig. 4. 



Discorbina orbicularis, Brady, 1884, FC, p. 647, pi. Ixxxviii, figs. 4-8. 



Discorbina orbicularis, Balkwill and Wright, 1885, DIS, p. 349, pi. xiii, figs. 31-3. 



Six stations: 388; WS 71, 84, 88, 89, 245. 



This species, so abundant in the West Indies and Pacific and also widely distributed 

 in higher latitudes, is strangely rare in the Falkland area. Moreover specimens are 

 small and not very typical. Not uncommon at WS 88, and almost equally good at 

 WS 245 ; a sessile specimen at WS 84. 



344. Discorbis tricamerata, sp.n. (Plate XIV, figs. 13-16). 



Three stations : 388 ; WS 88, 92. 



Test free, hyaline, plano-convex; a depressed cone of two convolutions only, each 

 consisting of three chambers rapidly increasing in size. On the dorsal side all the 

 chambers are visible; they are slightly inflated, and separated by somewhat depressed, 

 recurved sutural lines ; on the ventral side only the three chambers of the final convolu- 

 tion are visible, slightly turgid and curving inwards to a large elongate and deeply sunk 



16-2 



