94 CLEIDOTHAERUS. 
CIR’RUS. Sow. (Cirrus, atendril.) Fam. Turbinacea, Bl. & Lam. 
Descr. Spiral, conical, with an hollow, funnel-shaped axis; 
whorls contiguous, numerous, rounded, or slightly angulated. 
Obs. This fossil genus resembles Trochus, from which it is 
known by the deep, funnel-shaped umbilicus. Fig. 349, C. 
nodosus. 
CLAN’CULUS. Montf. Trocuus Pharaonis, &c. Lam. Obs. 
This, with several other species, belong more properly to Mono- 
ponta, Lam. Fig. 361. 
CLA’THODON. Conrad. Gwarsopon, Gray. 
CLAUSILIA. Drap. (Clausium, a valve or folding door.) Fam. 
Colimacea, Lam. Limacinea, Bl. Descr. Spire elongated, 
consisting of many volutions; aperture small, subquadrate, hav- 
ing several tooth-shaped folds on the columella. A small, elastic, 
shelly plate attached to the columella within, called the Clau- 
sium, its office being to enclose the aperture when the animal 
has retired within its shell. Obs. This last character distin- 
guishes it from the Pupz, to some of which it bears a very near 
resemblance. Hab. Land, in the southern part of Europe, seve- 
ral British species. Fig. 295. Clausilia Macascarensis. 
CLAU’SIUM. Aname applied to the beautiful contrivance whence 
the genus Clausilia derives its name, consisting of a little bony 
tortuous plate, placed in a groove on the columella. Here it 
serves the purpose of a door, which, when not operated upon by 
counteracting pressure, springs forwards on its elastic ligament 
and encloses the animal in his retirement. When he wishes 
to make his exit, he pushes back the Clausium into the groove. 
CLAVAGELLA. Lam. (Clava, a club.) Fam. Tubicole, 
Lam. Pyloridea, Bl. Descr. Two irregular, flattish valves; 
one fixed or soldered, so as to form a part of the side of 
an irregular shelly tube; the other free within the tube nearthe 
base. Obs. The shells composing this genus are found in stones, 
madrepores, &c. and appear to form the connecting link between 
Aspergillum, which has both valves cemented into the tube; 
and Fistulana, in ‘which both are free. Fig. 45, a fossil Cla- 
vagella. 
CLAVA’TULA. The generic name by which Lamarck originally 
distinguished those species of Pleurotoma which were remark- 
able for the shortness of their canal. In his system, however, 
they are re-united to Pleurotoma, fig. 381, P. Strombiformis. 
CLA’VATE. When one extremity of the shell is attenuated and 
the other becomes suddenly ventricose or globular, it is said to be 
Clavate. Ex. Murex Haustellum, fig. 396. 
CLAVULINA. D’Orb. A genus of microscopic Foraminifera. 
CLEIDOTHZ’RUS. Stutch. (Gatpos, hinge; Kwels, clavicle.) 
Fam. Chamacz or Myarie, Lam. JDescr. Inequivalve, irre- 
gular, solid, attached; with one cardinal, conical tooth in the 
