Recent and Fossil Foraminifera. 323 



One typical recent specimen of the type usually found in British 

 dredgings, in which all the chambers are of practically the same 

 diameter. This appears to be due to the large size of the primor- 

 dial chamber, and may possibly represent the megalospheric form 

 (if the shell. So far as our experience goes, the species is very rarely 

 fouDd in shore-sands, though frequent in shallow water dredgings 

 in temperate and tropical seas all over the world. With increasing 

 depth the shell displays a tendency to a rapid increase in the 

 diameter of the successive chambers, which thus become more or 

 less spherical in shape. This again is probably due to the initial 

 chamber being of the microsphere type, but it would require a 

 long series of careful measurements to verify this observation, 

 which we record without further comment. 



354. Marginulina glabra d'Orbigny. 



Marginulina glabra d'Orbigny, 1826, Ann. Sci. Nat., vol. vii. p. 259, No. 6; 

 Modele, No. 55 



Ditto. (d'Orbigny) Brady, 1870, Ann. and Mag. Nat. Hist., ser. 4, vol. vi. 

 p. 296, pi. xii. fig. 3. 



Ditto. (d'Orbigny) Brady, 1884, Foram. ' Challenger,' p. 527, pi. lxv. figs. 5, 6. 



Ditto. (d'Orbigny) Burrows, Siierborn and Baily, 1890, Journ. R. Micr. Soc, 

 p. 10, pi. x. fig. 1. 



Vaginulina glabra (d'Orbigny) Goes, 1894, Arctic and Scandinavian Fora- 

 minifera, pi. xi. figs. 659-661. 



Marginulina glabra (d'Orbigny) Flint, 1899, Keport U.S. Nat. Museum for 

 1897, p. 313, pi. ix. fig. 1. 



Ditto. (d'Orbigny) Millett, 1902, Malay Foraminifera, Journ. B. Micr. Soc, 

 p. 526. 



Several specimens, all fossil, and apparently from Tertiary 

 shell-sands. They represent the two most widely divergent types 

 of this extremely variable species, namely, those in which the 

 initial spirol portion is reduced to a minimum, and is followed by 

 a series of nodosarian chambers (compare 31. attenuata Neugeboren, 

 1851, Berh. Mitth. Siebenbiirgen Ver. Nat. Jahrg. ii., p. 121, pi. iv. 

 figs. 3-6) and those in which there is a distinct spiral portion, 

 followed by a few swollen and embracing Glanduline chambers. 

 This variable type has been recorded as far back as the Lias, and 

 is of frequent occurrence in the present day in dredgings at all 

 moderate depths. 



355. PoTymorphina acuminata d'Orbigny sp. 

 (Plate X. figs. 17, 18.) 



Pyrulina acuminata d'Orbigny, 1840, Mem. Soc. Geol. France, vol. iv. p. 43, 

 pi. iv. figs. 18, 19. Facsimile in Science Gossip, 1870, p. 157, 

 fig. 150. 



Ditto. (d'Orbigny) Eeuss, 1845-6, in Geinitz, Grand. Verstein, p. 670, 

 pi. xxiv. fig. 64. 



