rOEAMIJS^IFEEA OF THE KEEIMBA AECHIPELAGO. 603 



15 Stations. 



Fairly generally distributed, and frequent at some Stns., attaining its finest develop- 

 ment at Stns. 3 and 9. At Stn. 1 a specimen was observed in which the final 

 chambers were triangular in section instead of round. The variety passes almost 

 imperceptibly into P. arietinus. 



Subgenus Monaltsidium Chapman. 



117. Monalysidium polita Chapman. (Text-fig. 43, G.) 



Peneroplis lituus Brady, 1884, p. 205, pi. xiii. figs. 24, 25 (?). 



„ [Monalysidium) polita Chapman, 1899, FFA. p. i, pi. i. fig. 5 {see Millett, 1898, etc., 



FM. 1898, p. 613). 



12 Stations. 



Generally distributed, and of quite frequent occurrence at many Stns. The largest 

 and best specimens were at Stn. 3, and those at Stns. 1, 4, and 5 were not much inferior. 

 At Stn. IX the variety was represented by a single very small and curved specimen, 

 the walls of which were quite transparent and feebly punctate. At many of the Stns. 

 the specimens exhibited a sudden change in the size of the chambers, sometimes 

 increasing and at others decreasing rapidly in dimensions. Occasionally a decrease in 

 size of chambers was followed immediately afterwards by renewed increase. 



The majority of the specimens were flush at both extremities, which were furnished 

 with a central aperture, but at most Stns. some of the individuals were furnished at 

 one or both extremities with a produced neck bearing the aperture. This would 

 seem to show that growth can proceed equally at either extremity. Chapman has 

 instituted the subgenus Monalysidium for the Peneroplids of the lituus type, and, so 

 far as the specimens which he separates under the name of M. sollasi are concerned, 

 on what appears to be insufficient grounds. There appears to us to be no reason for 

 separating these specimens, which have a spiral initial portion, from the genus 

 Peneroplis, the variation from type not being much greater than is to be found in many 

 other lines of variation exhibited by that genus. As regards the moniliform tests 

 previously recorded and figured by Brady under the specific name P. lituus, and for 

 which Chapman proposes the name Monalysidium polita, we agree with the wisdom 

 of the separation, there being no evidence whatever in our minds of these forms 

 ever being furnished with a spiral initial portion such as Peneroplis must possess. 

 The Kerimba dredgings furnish numerous specimens comparable with his figure and 

 description of Monalysidium polita as figured in C. 1899, FFA. {ut supra), but we 

 must admit that Chapman has introduced an element of confusion by figuring in 

 a later paper (C. 1900, FLF. p. 180, pi. xix. fig. 8), under the name Peneroplis 

 [Monalysidium) politus (sic)], an entirely diflferent form having a well-marked involute 

 spiral test, not followed by any rectilinear series of chambers but ending in a' some- 



