690 MESSES. E. HEEON- ALLEN AND A. EAELAND ON THE 



or pleats in tlie inner or float-chamber, and that the float-chamber is adherent to the 

 balloon excepting at the lobulations and along the ramihcations of the arborescent 

 markings. (iii-) The absence in the vast majority of cases of the umbilical ento- 

 solenian tube by which in the normal C. bulloides the inner or float-chamber commu- 

 nicates with the balloon and thence with the surrounding medium, (iv.) The absence 

 of the coarse basal perforations on the balloon which are characteristic of the 

 typical C. bulloides. 



It would thus appear that in the typical C. bulloides the lower half of the shell 

 consists of two distinct hemispherical chambers, one suspended within the other, 

 without actual contact anywhere, the entosolenian tube of the balloon-chamber merely 

 fltting into the depression formed by the corresponding tube of the float-chamber 

 without actual fusion. In C. milletti, on the other hand, the internal float-chamber 

 is adherent to and is fused with the balloon-chamber, except at a number of places 

 where the four deep lobulations of the float-chamber pass Irom its upper peripheral 

 margin to the base of the test, ramifying as they go. These ramifying passages give 

 to the shell its typical wrinkled appearance. 



Again, Avhereas in the typical C. bulloides there are always two well-marked forms, 

 as already pointed out, C. milletti is, so far as we have observed, always acervuline 

 and within very narrow limits of variation constant both as to size, general appearance, 

 and colour. The test is always high-domed, and the acervuline chambers numerous 

 and regularly formed as compared with acervuline specimens of the typical C. bulloides. 

 Specimens are also in nearly all instances of a characteristic brown colour, and the 

 initial discorbine chambers are of the type of Dlscorbina concinna Brady. 



The distribution of C. milletti certainly extends all over the tropical Indo-Paciflc 

 area, but we have not met with it as yet in the tropical Atlantic. 



In the Brady collection at Cambridge there is a slide of C. bulloides from Levuka, 

 Fiji, which contains several specimens of this form. Brady's fig. 9, pi. cii. in FC 

 1884, sugijests this wrinkled form in its general appearance, though the essential 

 markings are not reproduced. 



Size variable — average specimens vary between -3 and "4 mm. in total height, 

 of which about '2 mm. represents the acervuline portion of the shell; breadth of 

 balloon-chamber averages "3 mm. 



DiscoEBiNA Parker & Jones. 



339. DiscorMna COra (d'Orbigny). 



Rosalina cora d'Orbigny, 1839, FAM. p. 45, pi. vi. figs. 19-21, (See also B. 1884, FC. 

 p. 627 ; and H.-A. & E. 1913, CI. p. 11 1, & Table p. 113.) 

 7 Stations. 



This very depressed and scale-like species occurs rarely. The only really typical 

 specimen was at Stn. ] X attached to a shell-fragment. This individual was of 



