CLAVATULA. 109 



CLAUSIUM. A name 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 prevented by 

 counteracting pressure, springs forward on its elastic ligament, 

 and encloses the animal in his retirement. The aperture is 

 opened by pushing back the clausium into the groove. 



CLAUSULUS. Montf. Conch. Syst. 1, 179. A genus of micro- 

 scopic Foraminifera. 



CLAVA. Humph. Cerithium, Lam. 



CLAVAGELLA Lam. (Clava, a club.) Fam. Tubieolse, Lam. 

 Pyloridea, Bl. — Descr. Two irregular flattish valves, one fixed 

 or soldered, so as to form part of the side of an irregular shelly 

 tube; the other free within the tube near the base. — Ohs. 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 Clavagella. Found recent 

 on the Coast of Malta and New South Wales. 



CLAVA LITHES. Sw. A genus composed of some fossil shells, 

 separated from the genus Fusus, which, having the general form 

 of Turbinella Rapa, &c. are considered by Swainson, as holding 

 an intermediate station between Fusus and the Turbinellidse. — 

 Descr. " Unequally sub-fusiform ; the body whorl, and spire, 

 being conic ; and the canal suddenly contracted and attenuated ; 

 terminal whorls papillary ; inner lip thick; pillar smooth, C. 

 longaevus, clavellatus, Nose, ponderosus, Sw." — Obs. The papil- 

 lary spire may form a sufficient reason for separating this genus 

 from Fusus, while the absence of plates on the columella places 

 them at a still greater distance from Turbinella. 



CLAVATE. 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. 



CLAVATULA. Lam. The generic name by which Lamarck ori- 

 ginally distinguished those species of Pleurotoma which were 



