NUMMULINIDAE 189 



511. Rotalia orbicularis (d'Orbigny). 



Gyroidina orbicularis, d'Orbigny, 1826, TMC, p. 278, no. i ; Modele no. 13. 

 Rotalia orbicularis, Brady, 1884, FC, p. 706, pi. cxv, fig. 6. 

 Gyroidina orbicularis, Cushman, 1918, etc., FAO, 1931, p. 37, pi. viii, figs, i, 2. 

 Six stations: 385; WS 469, 505, 506, 507 a, 507B. 



Frequent but small at St. 385 in 3688 m., and a single larger specimen at St. WS 469, 

 3959 m. Elsewhere rare except at St. WS 505 where it is frequent. The specimens here 

 and at the other Bellingshausen Sea stations, WS 506, 507 A, 507 b, are generally small 

 and far from typical. 



512. Rotalia soldanii, d'Orbigny (F 394A) (SG 328). 

 Eleven stations: 369, 384-6; WS 204, 205, 403, 468, 469, 493, 507 b. 



Frequent at several deep-water stations in the Scotia Sea and Drake Strait, Sts. 386, 

 WS 204 and 469; rare elsewhere. Particularly large specimens were found at Sts. 385 

 and WS 469, but the general average is rather small; the species is very small and 

 pauperate at Sts. WS 493 and 507 b. 



Family NUMMULINIDAE 



Sub-family NONIONINAE 



Genus Nonion, Montfort, 1808 



513. Nonion depressulus (Walker and Jacob) (F 399) (SG 329). 



Forty-four stations: 170, 175, 177, 180, 181, 186, 192, 194-6, 198, 202-4, 363, 377, 382, 386; 

 64°56'S, 64°43'W; WS 382-5, 391, 394-6, 476, 480-2, 484-6, 488, 493, 494A, 495, 497, 506, 

 507 A, 512-14. 



Generally distributed and occurring at all depths down to 4773 m., but the only 



stations at which it is common or frequent are under 1000 m., and it reaches its 



optimum development under 300 m. At greater depths it is very rare, often represented 



by a single specimen. The best stations are 181, WS 395, 476, 482 and 488. 



514. Nonion umbilicatulus (Walker and Jacob) (F 401) (SG 332). 



Thirty-eight stations: 170, 171, 175, 177, 180, 181, 186, 187, 190, 194-6, 200, 202, 206, 363, 369; 

 64°56'S, 64°43'W; WS 204, 383, 385, 386, 393-5, 476, 480, 482, 485-8, 493, 494A, 498, 505, 

 507B. 513- 



Never very common, but frequent at Sts. 180, WS 395 and 486, all of which are in 

 moderate depths, also at St. WS 204 in 3328 m. There is great variation in the extent 

 of the umbilical depression, the best specimens being from the deep stations, where the 

 species passes almost imperceptibly into A^. pompilioides . 



515. Nonion pompilioides (Fichtel and Moll) (F 402) (SG 333). 

 Nine stations: 383-6; WS 205, 403, 468, 469, 472. 



Frequent at Sts. 384, 385, 386, WS 468 and 469 ; very rare at the other stations. All of 

 them are over 3500 m. 



516. Nonion stelliger (d'Orbigny) (F 404) (SG 335). 



Twenty stations: 170, 175, 177, 180-2, 190, 196, 200, 363, 366; WS 377, 471, 481, 482, 486, 490, 

 493. 494A, 506. 



Frequent at St. 190, rare or very rare elsewhere, often only a single specimen. The 



