412 DISCOVERY REPORTS 



D .vilardehoana . Their sizes range between 0-25 and 0-50 mm. which alone would exclude 

 them from D. isabelleana. 



It is fortunate, in the circumstances, that the original Types have survived in good con- 

 dition. The Type tube labelled " Rosalina Isabelleana, lies Malouines" contains seven 

 specimens of varying sizes; the largest, when perfect, probably exceeded 3 mm. in dia- 

 meter. They represent a form with which we had become very familiar in the examination 

 of our material, without, up to that time, associating it with d'Orbigny's figure. The 

 definite punctation shown in the figures had misled us, as it had done others. 



Apart from this punctation the figures, though weak, are not faulty, though they give 

 a poor impression of a large and handsome species. They also fail to convey the fact, 

 also overlooked in the descriptions, that the dorsal surface of the chambers, though 

 sometimes smooth, is generally more or less roughened with studs of solid shell sub- 

 stance, which occasionally merge to form ridges of ornament approaching those found 

 in Heronalletna {Discorbis) kempii. The perforations on the other hand are extremely 

 minute, the shell being quite glassy in spite of its thickness. 



The colour to which d'Orbigny alludes, "d'un rose violace", has almost completely 

 faded from the Types, but is a very noticeable feature in fresh specimens from our 

 material. It is due to the chitinous lining of the chambers. 



There can be no doubt that d'Orbigny's species is a well-marked and definite type. 

 Beyond the few incorrect records which we have noted supra it appears to have no 

 history as isabelleana. But we suspect that some records of Pulvinulina repanda var. 

 concamerata, and possibly of Pulvinulina punctulata, would have been more correctly 

 assigned to the species under consideration. 



339. Discorbis turbo (d'Orbigny). 



Rotalia {TrochuUna) turbo, d'Orbigny, 1826, TMC, p. 274, no. 39, IModele no. 73. 



Discorhina turbo, Brady, 1884, FC, p. 642, pi. Ixxxvii, fig. 8. 



Discorbina turbo, Sidebottom, 1904, etc., RFD, 1908, p. 11, pi. iii, figs, i, 2. 



Fifteen stations: 48, 51 ; WS 77, 83, 84, 86, 87, 88, 89, 91, 97, 99, 225, 245, 248. 



Generally distributed, often quite frequent. It attains a large size and very fine 

 development at several stations, especially 48, WS 84 and 88. Limbate forms pre- 

 dominate at some stations, notably WS 83 and 248. No Type to be found in Paris. 



340. Discorbis nitida (Williamson). 



Rotalina nitida, Williamson, 1858, RFGB, p. 54, pi. iv, figs. 106-8. 

 Discorbina nitida, Sidebottom, 1904, etc., RFD, 1908, p. 13, pi. iv, fig. 6. 

 Discorbina nitida, Heron-Allen and Earland, 1916, FWS, p. 269, pi. xlii, figs. 26-30. 



Ten stations: 51, 388; WS 87, 88, 89, 90, 91, 92, 221, 408. 



Generally distributed, often very common. The best at WS 87, 88, 89, 90, par- 

 ticularly at WS 88. The Falkland type is rather more concave on the oral side than in 

 British specimens, but has all the other characteristics of Williamson's form. 



