Recent and Fossil Foraminifa-a. 445 



169. Discorbina trochidiformis Laniark sp. 



Botalites trochidiformis Lamarck, 1804, Ann. Mus., vol. v. p. 184; and 1806, 



vol. viii. No. 1, pi. Ixii. fig. 8 a, b. 

 Discorbina trichidiformis (Lamarck) Jones, 1878, Dixon's Geology of Sussex, 



2nd ed., p. 172, pi. ix. (10) fig. 6. 

 Botalina trochidiformis (Lamarck) Terquem, 1882, Mem. Soc. Geol. France, 



ser. 3, vol. ii. Mem. III. p. 68, pi. vi. fig. 2. 



Fossil. Large specimens, apparently derived from the Mixon 

 Kocks, are of frequent occurrence in the coarser gatherings. 

 Millett describes it as " common." 



170. Discorbina allomorphinoides Eeuss sp. 



Valvulina allomorphinoides Eeuss, 1860, Sitz. k. Akad. Wiss. Wien, vol. xl. 



p. 223, pi. xi. fig. 6. 

 Discorbina allomorphinoides (Eeuss) Brady, 1884, Foram. 'Challenger,. 



p. 654, pi. xci. figs. 5, 8. 

 Ditto. (Eeuss) Millett, 1903, Journ. E. Micr. Soc. p. 703. 



Frequent; fossil. Eeuss's specimens were from the Chalk, 

 but these are apparently of a more recent, and probably Tertiary 

 origin. 



171. Discorbina cristata sp. n. 

 (Plate XVIII. figs. 8-10.) 



We have found three specimens of fossil origin which we have 

 been unable to identify with any published description within our 

 knowledge, and we propose for them the specific name D. cristata, 



Description. — Shell a rotaline spiral of about nine chambers 

 arranged in two convolutions, the chambers rapidly increasing in 

 size. The superior face but slightly convex and very rough in 

 appearance, due to a thickening of the shell wall, which rises like 

 a crest on each inflated chamber. The inferior face presenting 

 only the five chambers of the last convolution, and opening in the 

 centre into an umbilical cavity, which apparently extends to all the 

 chambers of the test. The inferior side, which is covered with fine 

 striae radiating from the central umbilicus, is comparatively smooth, 

 the depressions between the several chambers being very slight. 



We cannot state whether the curious umbilical cavity is a 

 normal feature of the shell, or merely due to a dissolution of the 

 internal septa, such as has been described by Eaiiand* as occurring 

 in the reproductive stages of some recent Discorbina from the 

 adjacent shore-sands of Bognor. A similar dissolution can be 

 observed in many specimens of the genus Polymorjphina, and has 



* Earland, The Foraminifera of the Shore-sands of Bognor, 1905. Journ. 

 Quekett Micr. Club, ser. 2, ix. No. 57, pp. 221-3'. 



