700 MESSES. E. HEEON-ALLBN AND A. EAELAND ON THE 



into the asterigerine chambers, each of which has also a special secondary opening in 

 the shape of a tubular extension, which passes through the adjacent chamber of the 

 superior series and so communicates with the next asterigerine chamber, finally 

 opening into a broad funnel-shaped depression on the oral face of the final chamber. 



This highly complex structure will be more apparent from the two diagrammatic 

 figures which we publish. They show balsam-mounted specimens in optical section 

 (as viewed from the upper and lower sides) in which the asterigerine chambers of the 

 last whorl only are shaded, while the principal chambers remain clear. 



The purport of this unique structure is not obvious, but it is evident that the double 

 series o{ apertures and the immediate opening of the chinks into the asterigerine 

 chambers must greatly fiicilitate the access of the protoplasm to the surrounding 

 medium and so facilitate nutrition. This is borne out by the fact that many specimens 

 exhibit food-contents of relatively immense size in the protoplasm remaining in the 

 chambers. 



The so-called retral processes, which are really struts of solid shell-substance, are 

 poorly developed in most of the Kerimba specimens, and are often confined to the 

 peripheral margin of the test, the chinks on the superior surface being uninterrupted. 



365. DisCOrbina rimosa Parker & Jones. 



Discorbina rimosa Carpenter, Parker, & Jones, 1862, IP. p. 205. 



„ Parker & Jones, 1865, NAAF. pp. 385, 421, pi. xix. fig. 6. 



„ Brady, 1884, FC. p. 642. 



„ Millett, 1898, etc., FM. 1903, p. 702, pi. vii. fig. 7. 



1 Station. 



One specimen only, resembling Millett's figure of this species, which, it may be 

 remarked, diff'ers considerably from the original figure published by Parker and Jones. 

 This represents a shell with a smooth surface, although their description states that 

 " the pores are large and the shell-substance thick." These features are more highly 

 brought out in Millett's figure. Parker and Jones, in describing D. polystomelloides 

 (P. & J., NAAF. p. 421, pi. xix. fig. 8), state that it may be regarded "as a granular 

 form of I), rimosa, but larger, more symmetrical, and extremely rough." It appears 

 to us somewhat doubtful whether it is expedient to separate the two forms — D. rimosa 

 is probably only a depauperate form of D. polystomelloides. 



366. Discorbina rarescens Brady. 



Discorbina rarescens Brady, 1884, FC. p. 651, pi. xc. figs. 2, 3, & ? 4. 

 „ „ Egger, 1893, FG. p. 388, pi. xv. figs. 45-47. 



„ „ Chapman, 1900, PLF. p. 192. 



„ „ Heron-Allen & Earlaud, 1908, etc., SB. 1909, p. 443. 



2 Stations. 



Two small but fairly typical specimens at Stn. 7, and many at Stn. 11. 



