334 Transactions of the Society. 



"Test discoidal, thicker in the centre than at the edges, where 

 one sees only two annular rows of chamberlets. Test rough by 

 reason of little prominences which stand up between the per- 

 forations. 



" Habitat.— Upper Eocene of Bruges (Gironde). Rather rare. 



" Observations. — In its exterior aspect this fossil closely resem- 

 bles an Orbitoides or a Cycloclypeus. It differs from the former in the 

 absence of chambers in the thickness of the central boss, and from 

 the latter in the absence of the system of partitional canals and 

 the compact pillars which traverse the test." 



There are several points in M. Schlumberger's description with 

 which we cannot agree. As seen in horizontal section, our speci- 

 mens commence with a regular llotaline spiral of about 2 to 3 whorls. 

 There are 8 to 10 chambers in the last convolution, and up to 

 this point the chambers are fairly regular in size. Subsequent 

 chambers are added in more or less regular annuli and vary con- 

 siderably in size and shape. The earlier annuli have apparently 

 simple walls, i.e., each chamber consists of a semicircular wall 

 secreted over the outer surface of a bead of protoplasm, which had 

 been protruded through the tubuli of an earlier chamber. Later 

 on the chamberlets appear to have compound walls, i.e., the pro- 

 truded bead of protoplasm secreted a basal wall of its own, sepa- 

 rating it from the wall of the preceding annulus. This double cell- 

 wall gives the appearance of a wavy line of chambers, referred 

 to by Schlumberger and illustrated by him diagrammatically. 



We have been unable to trace any direct communication between 

 adjacent chamberlets of the same or adjacent convolutions. The 

 horizontal sections show no trace of any tubuli in the partition 

 walls or any definite oral aperture. If any tubuli are present in 

 the side walls of the chambers they must be extremely minute, as 

 they are not visible under J-in. objective. Vertical sections, how- 

 ever, show that the top and bottom walls of every chamber were 

 perforated with coarse tubuli, extending right through the thick 

 deposit of shell-substance to the external surface. It would, there- 

 fore appear that each chamberlet was a separate and self-contained 

 unit so far as nutrition was concerned, and that the growth of the 

 shell depended on extrusions of protoplasm through these aper- 

 tures, which formed at first isolated chambers round the rim and 

 subsequently a tube with constrictions at intervals. The whole 

 question is, however, so difficult to follow owing to the friability 

 of the test and the trouble of preparing sections, that we put for- 

 ward our conjectures with some diffidence. 



We are unable to confirm Schlumberger's statement that " the 

 partition walls of each circle of chambers extend towards the centre 

 above the already formed chambers." If this were the case a vertical 

 section would show strong bands of clear shell-substance cutting 



