178 CLASS III. GASTEROPODA. ORDER VII. PECTINIBRANCHIATA. 
a regular spire, with the apex somewhat sharp, though it is sometimes 
eroded, or decollated ; the aperture is semicircular, or oblong ; the colu- 
mella, which is arched, has a somewhat spiral, often reflected fold, form- 
ing the upper margin of the canal ; and the lip is generally thickened, and 
sometimes widely reflected. 
Examples. 
Pl. CCXXVI. Fig. 1. 
CERITHIUM BREVICULUM, Sowerby, Genera of Shells, No. 42. Kiener, 
Iconographie des Coquilles vivantes, pl. 15. f. 4. 
Pl. CCXXVI. Fig. 4. 
CeRITHIUM TUBERCULATUM, Lamarck, Anim. sans vert., vol. vil. p. 75. 
Martini, Conch., vol. iv. pl. 157. f. 1490. 
Cerithium moros, Bruguiére. 
Strombus tuberculatus, Linneus. 
Pl. CCXXVI. Fig. 5. 
CERITHIUM vaRicosuM, Sowerby, Genera of Shells, No. 42. 
Pl. CCXXVI. Fig. 8. 
Crriruium Soversi*, Kiener, Iconographie des Coquilles vivantes, 
pleyete2: 
Cerithium clava, Gray. 
Pl. CCXXVI. Fig. 9. 
Creriturum Paciricum, Sowerby, Genera of Shells, No. 42. 
Pl. CCXXVII. Fig. 2. 
CrriTHIUM DEcoLLatTuM, Bruguiére, Dict., No. 45. Lamarck, Anim. 
sans vert., vol. vil. p. 71. 
Murex decollatus, Linnzus. 
* The word clava was preoccupied by Lamarck in reference to a fossil species of this genus. 
