Thuramviina papillata Brady : a Study in Variation. 543 



Thurammina papillata Brady. 

 Type, " Orbuline Lituola" of Carpenter (Eefs. 1 and 5). 

 Plate XXVI, figs. 1-13. 



In the figure of an " Orbuline Lituola " figured by Carpenter in 

 1875 (The Microscope, Eef. 1), we have the original type on which 

 Brady subsequently founded (Eef. 2) his species Thurarnmina papil- 

 lata, and the figure fortunately represents an organism of very con- 

 stant shape and of world-wide distribution, and is therefore pecu- 

 liarly fitted to retain its position as the central type of the genus. 

 Carpenter's figure represents a perfectly spherical thin-shelled test 

 built up of many minute sand-grains, accurately fitted together in 

 a mosaic by a ferruginous cement which gives to the test a well- 

 marked colour, ranging between pale lemon and dark brown, but 

 is never present in sufficient quantity to mask the constituent 

 sand-grains or give a Trochammine finish to the surface, which is 

 always slightly rough and unpolished. The surface of the sphere 

 is beset with a variable number of papillae, projecting but little 

 from the surface and distinctly pert orate. This original figure, 

 resembling our figs. 3-6, PL XXVI, we propose to retain as T. 

 papillata Brady type. It is to be regretted that Brady, although 

 identifying his species papillata with Carpenter's earlier published 

 figure, did not adequately figure Carpenter's type either in 1879 or 

 1884. His figure 7 (Eef. 12) was perhaps intended to represent 

 the typical sphere type, but really represents a characteristic form 

 with imperforate papillae to which we refer post. Brady's other 

 figures represent more or less abnormal forms. 



Starting from this central type, variation begins and progresses 

 in many directions, according to the nature of the shell-wall, the 

 number of its papillae, their shape and size, etc. 



Variation in Wall of Sphere. Chitinous and 

 SuB-CHiTiNous Forms. 



At "Goldseeker" Stn. ix B, 61° 34' N. 2° 9' E. (330 metres), 

 where the type is fairly frequent, we find an interesting series of 

 specimens in which the original chitinous wall is retained without 

 traces of arenaceous investment. They are usually of a violet or 

 purple colour with characteristic papillas, and generally without 

 visible protoplasmic contents (PI. XXVI, figs. 7, 8). The chitin 

 varies considerably in thickness, but is usually so thin that the 

 sphere has more or less collapsed in drying. Such specimens occur 

 in less numbers at other stations. 



Proceeding from these purely chitinous forms, some specimens 

 of which equal in size the normal type as found at this Station, 

 emerge a whole series in which an investing shell has been 

 secreted without the use of constituent visible sand-grains. Such 



