Thurammina papillata Brady : a Study in Variation. 545 



Thurammina papillata var. castanea var. nov. 

 Plate XXVI, figs. 14-18, and Plate XXIX, fig. 17. 



As opposed to the last described form, in which the imperforate 

 papilhie are practically flush witii the wall of the sphere, we have 

 from many localities a variation which may be referred to 

 Haeusler's figure 7 (Eef 21, pi. vi), and for which we propose the 

 varietal name castanea, because the shell is covered with large 

 conical papillae, set closely all over tlie sphere like the spines on a 

 horse-chestnut. Such specimens often attain large size and a com- 

 paratively coarse arenaceous investment, but minute specimens are 

 also to be found, also all transition forms, from the purely chitinous 

 to coarsely arenaceous. Brady's curious figure 9 (Eef. 12, pi. 

 xxxvi.) may probal^ly represent a variation of this form, in 

 which the numerous spinous papillae are confined to one half of 

 the sphere. Specimens intermediate between the smooth and 

 spinous spheres in all stages of size are to be found. It must be 

 distinctly understood that we use varietal names in a taxonomical 

 sense only. They have no biological significance. 



Vakiations fkom the Sphere Type. 



Turning to variations in shape from the sphere we find our- 

 selves in a maze of forms, some of which can be dismissed with 

 brief notice, while others call for more attention. 



Thurammina hemisphmrica Haeusler (Eef. 9, pi. iv, fig. 14), 

 may, we think, be dismissed with scant ceremony and the specific 

 name discarded. Thurammin[e in the attached condition are, in 

 our experience, of rare occurrence, but like many Arenacea, T. 

 papillata at times assumes the sessile condition, and as such 

 becomes, of course, hemispherical. We have met with such speci- 

 mens (PI. XXVII, fig. 1), but see no object in retaining even a 

 varietal name for sessile individuals. 



Thurammina papillata var. compressa Brady. 



Type, T. compressa Brady (Refs. 2 and 12). 



Plate XXVII, figs. 2-8. 



Thurammina compressa Brady is in a different case, and to 

 some extent a distinctive form and worthy of retention as a varietal 

 name. The variety is characterized by the presence of compara- 

 tively large papillae, situated round the marginal edge of a flattened 

 sphere, and originates in the compression of the ty^^e sphere at the 

 two poles and the suppression of the papillae, except those on the 

 equatorial ring, which become largely developed. Such suppres- 

 sions of the papillae would result as a matter of course from com- 

 pression of the sphere, as the papillae on the nuirginal edge of 



