142 BOOK OF SPECIES. 
NODOSARIA. 
Elongated, straight or slightly arched, sub-conical, 
nodular; nodules globular, very smooth ; cham- 
bers formed by transverse septa, perforated in 
the centre or near the margin. 
N.RapicuLa. Nearly straight, a little taper- 
ing; joints transverse; chambers sub-cylindric, 
eight or nine. ;4- B. W. 13. 27. 
To" 
SPIRULA. 
Cylindrical, thin, almost transparent, white or pearl- 
colour, multilocular, partly twisted into a dis- 
coidal spiral; whorls distant from one another, 
the last produced in a straight line; septa 
transverse, placed at equal distances from each 
other, externally concave ; siphon lateral, inter- 
rupted; aperture orbicular. 
S. pEronit. W. Nautilus. 13. 16. 
CRISTELLARIA. 
Shell semi-discoid, multilocular ; whorls contiguous, 
simple, progressively enlarging ; spire eccentric, 
sub-lateral; septa imperforate. 
C. squaAmuLaA. W. 14.47. 
