FOEAMINIFEEA OF THE KEEIMBA ARCHIPELAGO. (389 



13 Stations. 



Almost universallj' distributed. It occurs as usual in two vei-y distinct types — 

 a small form in which the early chambers are arranged on a discorbine plan, and 

 a larger form in which a few discorbine chambers are succeeded by numerous 

 acervuline chambers before the formation of the balloon. The two forms nearly 

 always occur together, but in varying proportions. At some Stns., especially at 

 Stns. 2 h and 1 X, the discorbine type is the more abundant, at others the proportions 

 are either equal or with a predominance of the acervuline type. In the discorbine 

 type the balloon-chamber is often more or less elongated, so that the shell represents 

 a cylinder with convex extremities. In the acervuline type, on the other hand, the 

 whole test is usually more or less globular in form, the balloon representing one 

 hemisphere or, perhaps, rather more. There is at certain stations a tendency to 

 vertical compression of the test, the balloon being pronouncedly flattened — this is 

 notably the case at Stn. 8. Lateral compression, on the other hand, is extremely 

 rare, although instances were observed at several Stns. 



The dual nature of the terminal chamber as an outer or balloon-chamber and an 

 inner or float-chamber was first recorded by Earland in 1902, and forms the subject 

 of a principal section of the paper above referred to. 



338. Cymbalopora milletti, sp. n. (Pi. LI. figs. 32-35.) 



Cymbalopora bidloides Mihett, 1898, etc., FM. 1903, p. 697, pi. vii. fig. 4. 

 15 Stations. 



The curious type figured by Millett in his Malay Monograph as a variety of 

 C. bulloides occurs at practically all the Stns., and often in considerable numbers, 

 even where the typical C. bulloides is wanting. We propose to raise it to specific 

 rank and to associate it with the name of its author, being convinced, after a protracted 

 examination, that the type possesses essential and constant idiosyncrasies. This 

 decision has been arrived at after a careful examination, not only of our own specimens 

 from all over the area of its distribution, but also of a large number of slides, prepared 

 on board H.M.S. 'Challenger' by the late Sir John Murray and placed by him at our 

 disposal. 



The main points of distinction between the two forms may be summarized as 

 follows :— (i.) The rotaline portion is invariably high-domed and mainly acervuline, 

 consisting of a small but well-marked rotaline commencement followed by a number 

 of small but regularly formed acervuline chambers. (ii.) The balloon-chamber 

 presents a curiously wrinkled surface, and in its most typical condition the balloon 

 is superficially divided into four segments by arborescent markings originating from 

 four equidistant points on the peripheral margin of the balloon. Viewed as a 

 transparent object in balsam, it appears that these arborescent markings, which give 

 the balloon-chamber its peculiar wrinkled appearance, are occasioned by constrictions 



5 D 2 



