FROM THE FUNAFUTI ATOLL. 23 
B, are much more numerous than the specimens which link them 
together in the intermediate stages of growth; and this seems to 
be further corroborated by the internal shell-structure, which 
shows an apparent resting-stage in the shell-development, 
bounded by an irregular periphery, which differs from the 
broken and subsequently repaired rings of chamberlets. 
Description * :— 
Form A (megalospheric form).—Test discoidal, outline circular, 
or nearly so; the central area umbonate or biconvex, in full- 
grown specimens occupying about one-third the entire diameter 
of the shell. The initial series of chamberlets are enclosed in a 
secondary growth of shell-substance which gives rise to the um- 
bonate shape of the central area of the disc. Beyond the central 
thickened area the annuli of the chamberlets are thin and com- 
pressed, forming a broad flange around the centre. For the 
first two or three annuli the chamberlets are approximately 
square, or even laterally elongated, but they subsequently become 
more radially elongated, not to so great an extent, however, as in 
the microspheric form next described. 
Diameter of test 7, inch to 75 inch. 
The megalosphere of a typical specimen of form A from 
Funafuti measured 260 x 240. It is ovate, with one end 
pointed and the other rounded, and it lies in the concave sides 
of two crescent-shaped chambers, following upon which are the 
annuli of small chamberlets f. 
The nucleus observed by Lister was seen in one case to 
occupy the megalosphere, and in another it was found in the 
second chamber; that in the megalosphere was of an oval shape, 
measuring 60x40, whilst the nucleus seen in the second 
chamber was nearly spherical, measuring about 85 » in diameter. 
In the specimens from Funafuti which I decalcified and stained 
with picro-carmine no nucleus was observed in the central area 
of the disc, but irregular and ovoid nuclear bodies were seen 
in the last series of annuli, in many cases extending through 
an adjacent chamber. The structure of the nucleus was 
somewhat granulate with darker enclosures, like those observed 
by Lister. 
* ‘Dr. Brady’s description of the young of form A (= C. Guembelianus, Brady) 
now applies to the central’ area of the disc of full-grown specimens of the 
megalospheric type. See p. 751, Rep. Chall., vol. ix. 1884. ; 
t See also Lister, op. cit. p. 438. 
