134 DISCOVERY REPORTS 



both A and B are visible, A occupying most of the field of view. Seen from the other 

 edge A only is seen. On the ventral side only A and the final chamber of B are exposed. 

 The apertural face is very large and flattened, occupying nearly half of the ventral view^. 

 At least seven-eighths of its area represents the final chamber of ^ ; a small triangle on 

 its inner edge shows the final chamber of B. A is divided by a deep cleft running from 

 its inner edge well into the middle of the apertural face ; the walls of the cleft extend 

 inwards and are connected to the apertural face of ^'s previous chamber. The cleft 

 does not open into the cavity of ^'s chamber at all, the real aperture being an incon- 

 spicuous arch on the inner edge of the face, just over the exposed portion of 5. B has 

 no external aperture but is connected by an internal tube with the side of the cleft in A. 

 This and much of the structure is only visible in balsam-mounted specimens. 



Viewed as an opaque object the apertural face of Pseudobulimina is that of a typical 

 Ceratobidimina ; the exposed portion of 5 is so small that it might be overlooked. Viewed 

 from the dorsal side or from one edge the two series of chambers are conspicuous. 



The genus is based on the specimens discovered first by Chapman and subsequently 

 by Heron-Allen and Earland in the Ross Sea, and referred by both to Bulimina. The 

 similarity in external form to B. contraria (Reuss) was observed by both authors, but the 

 biserial arrangement of chambers in their specimens excluded that species from con- 

 sideration. B. contraria had been made the genotype of Ceratobidimina by Toula in 

 191 5, and many species have since been described, mostly fossils. The Antarctic speci- 

 mens are so like Ceratobulimina, except in the possession of the second series of 

 chambers, that I was at first inclined to regard these as of little importance, and likely 

 to exist in some of the described species of that genus. But after a careful examination 

 of all the species to be obtained, for many of which I have to thank Mr W. J. Parr 

 of Melbourne, and Mrs H. J. Plummer of Austin, Texas, I have been unable to find 

 any with even a vestigial trace of the second series. Dr Cushman also informs me that 

 he has never seen a second series in Ceratobulimina. 



282. Pseudobulimina chapmani (Heron-Allen and Earland) (Plate VI, figs. 11-14). 



Bulimina seminuda, Chapman (wow Terquem), 1914, EDRS, p. 29, pi. ii, fig. 9 and p. 43, pi. v, 

 fig. 6. 



Bulimina chapmani, Heron-Allen and Earland, 1922, TN, p. 130, pi. iv, figs. 18-20. 

 Robertina chapmani, Wiesner, 193 1, FDSE, p. 124, pi. xx, fig. 239. 



Six stations: 170, 175, 181, 190, 363; WS 482. 



Not infrequent at Sts. 170 and WS 482, rare elsewhere. Most of the specimens are in 

 perfect condition, and it was possible to make balsam preparations which disclosed the 

 internal structure. 



The stations are strung out in a line from St. 363 in the South Sandwich Islands, 

 through St. 170 off Clarence Island to the Bransfield Strait and Palmer Archipelago, 

 depths ranging between 93 and 342 m. Chapman's specimens were from an elevated 

 deposit probably laid down in over 100 fathoms ; the Terra Nova specimens from depths 

 down to 300 fathoms in the Ross Sea; Wiesner's from Kaiser Wilhelm's Land, 380- 

 385 m. There are no other records yet, but I hear from Mr W. J. Parr that it is common 



