POEAMINIFEKA OF THE KEEIMBA AECHIPELAGO. 711 



3 Stations. 



One broken specimen at Stn, \ B, and several perfect specimens at Stns. 11 and ■? A. 



395. Truncatulina glabra, sp. n. (Pi. LII. figs. 41-47.) 



14 Stations. 



Test nearly spherical, consisting of about two to tlrree convolutions of chambers ; 

 three to four chambers in the last convolution, which is inclined at an angle to the 

 axis of the preceding ones, so that the early convolutions are almost, or entirely, 

 enclosed. Shell-wall somewhat thick, but much thinner than in T. echinata Brady, 

 and coarsely perforate. Sutural lines depressed. Aperture situated in a depression 

 at the junction of the terminal chamber with the preceding convolution, usually a 

 simple crescentic slit, sometimes furnished with a rim or a short neck as in 

 T. echinata. 



The general aspect of this shell, both as an opaque object, and still more when 

 viewed as a transparent object in balsam, suggests a relationsliip with Splueroi- 

 dina buUoides d'Orbigny, but the rotaline formation of the chambers in very young 

 shells, such as we figure, and the tendency in very large mature specimens to develop 

 an everted rim to the aperture, tend to confirm its close affinity to T. edmiata, of 

 which ifc may be regarded as a smooth and depauperate variety. 



It occurs in company with T. echinata and usually in equal proportions at most 

 Stns., but at some Stns. it exhibits a preponderance and development which are very 

 striking. 



We have already found this form in shallow-water dredgings off Tahiti, so that it 

 probably extends across the tropical Indo-Pacific area in suitable depths. 



Brady was unquestionably well acquainted with this smooth type, but apparently 

 regarded it as merely a stage in the life-history of the allied form T. echinata. His 

 description of that form refers to it as " usually more or less beset with short blunt 

 spines or tubercles." His slide of T. echinata in the Brady Collection at Cambridge, 

 curiously enough, contains hardly any typically spinous individuals, but large numbers 

 of typical T. glabra in all stages; his fig. 12 (pi. xcvi., FC.) represents an almost typical 

 T. glabra, there being only a faint tendency to spinous development. 



Diameter in all directions averages about 0-2 mm, 



396. Truncatulina echinata Brady. (PL Llll. fig. 1.) 



Ptanorbulina echinata Brady, 1879, etc., RRO. 1879, p. 283, pi. viii. fig-. 31. 

 Truncatulina echinata Brady, 1884, FC. p. 670, pi. xcvi. figs. 9-14. 



Egger, 1893, FG. p. 403, pi. xvi. figs. 40, 41. 



MiUett, 1898, etc., FM. 1904, p. 490. 



lij Stations. 



Universally distributed except at Stn. 7, and usually moderately abundant. 

 VOL, XX. — PART XVII. No. 22. — Novemher, 1915. 5 a 



