32 CRYPTELLA. 
ribbed, waved or covered with spines; interior concave, smooth, 
with a flattish septum reaching nearly half across the cavity. 
Epidermis light brown. Obs. The difference between this genus 
and Calyptrea is that in the latter, the septum is more free from 
the sides of the shell, so that, instead of forming a regular plate 
covering half the aperture, it assumes a variety of shapes, and in 
some is cup-shaped, in others forked, and in others, forms a 
little angular shelf. Indeed the variations are so numerous, that 
I think it would be better to throw the two genera into one and 
then divide them into smaller groups. Fig. 239. 
CREPIDULI'NA. Bl. Cristetiaria, Lam. Microscopic. 
CRE'SEIS. Rang. Fam. Pteropoda, Lam. Descer. Thin, fra- 
gile, transparent, pyramidal, pointed; with a dorsal ridge pro- 
duced into a point at the edge of the aperture. Obs. The 
species found in the Mediterranean, is named C. Spinifera, (fig. 
222,) from its resemblance to a thorn. 
CREU’SIA. Leach. (Creux, se. Fr.a cavity.) Fam. Balanidea, 
Bl. Order, Sessile Cirripedes, Lam. Descr. Four valves 
composing a compressed cone, supported on, and jointed to, 
a cup-shaped cavity formed in the madrepore, in which it resides. 
Aperture quadrilateral, closed by an operculum of four valves. 
Obs. This genus is distinguished from Pyrgoma, which is sup- 
ported on the edges of a similar cup-shaped cavity, by the paries 
consisting of four valves, whereas in Pyrgoma it is composed of 
one single piece. Fig. 28,C. Gregaria. 
CRICOSTOM ATA. Bl. The second family of Asiphoni- 
branchiati, Bl. containing the genera Pleurotomaria, Delphi- 
nula, Turritella, Proto, Scalaria,.Vermetus, Siliquaria, Magilus, 
Valvata, Cyclostoma, Paludina. 
CRIOCE’RATITES. A genus composed of species of Ammo- 
NITES with disconnected whorls. C. Duvallii, fig. 482. 
CRI'OPUS. Poli. Crawnta, Auct. 
CRISTA’CEA. Lam. The third family of Polythalamous Ce- 
phalopoda, Lam. containing the genera Renulina, Cristellaria 
and Orbiculina. 
CRISTA’CEA. Bl. The third family of Polythalamia, Bl. con- 
taining the genera Crepidulina, (Cristellaria, Lam.) Oreas and 
Linthuris. 
CRISTARTIA. Schum. Dresas Plicatus, Leach. Anodon Tuber- 
culatus, Fer. 
CRISTEL’LARIA. Lam. Crepipunina, Bl. Fam. Cristacea, 
Lam. Descr. Semidiscoidal, chambered; whorls contiguous, 
simple, enlarging progressively; spire excentric, sublateral; 
septa imperforate. Microscopic. 
CRYPTELLA. Webb. Terstacettus Ambiguus of Ferussac. 
Published in Sowerby’s Genera of Shells as Parmaceiia Caly- 
culata. Descr. A small patelliform shell, with a very short pa- 
pillary spire, and the aperture irregularly expanded. Fig. 256. 
