Cerithium. MOLLUSCA. CERITHIADiE. 357 



Trans, vii. II7. t. xi. f. 2 Murex def. Sower. Min. Conch, t. ccccxi. f. 1 — 



In London Clay. 



8. T. sexdentatitrS Ovate acuminated, costated, longitudinally, striated, 



transversely carinated ; whorls convex ; aperture elongated, with five or six 

 teeth within its outer lip — Murex sex. Soiver. Min. Conch, t. ccccxi. f. 3. — 

 Marine formation, Colwell Bay, Isle ofWight. 



cerithiadj:. 



a. Marine. 



Cerithium. 

 (Strutheolaria.) 



ah. Fluviatile. 

 Potamedum. 

 Melanopsis. 

 (Pirena.) 



Gen. LXXXII. CERITHIUM.— Outer margin of the aper- 

 ture rounded, with an obsolete canal, in many species, at its 

 retral junction with the body-whorl, 



352. C. costatum. — Whorls ten, a spiral line at the base of 

 each, becoming double on the body-whorl. 



(Strombiformis costatus, Da Costa, Brit. Conch. 118. t. viii. f. 14.) Strom- 

 bus cost. Don. Brit. Shells, t. xciv. Mont. Brit. Shells, 255 English 



coast, rare. 

 Length about half an inch ; brown ; tapering to a fine point ; transverse 

 ribs numerous, rounded, slightly waved ; aperture ovate ; the outer Up a lit- 

 tle expanded ; inner lip smooth ; canal very short and patulous. 



353. C. turhiforme. — Whorls seven, destitute of a thread-like 

 spiral line at the base of each. 



Mont. Test. Brit. Sup. 110. t. xxx. f. ^ — Found by Mr Laskey on the 

 shores of Nun's Island, lona. 

 Length about a quarter of an inch ; breadth two-thirds less ; brown ; aper- 

 ture white ; whorls well-defined by the separating line ; transverse ribs about 

 eighteen ; base smooth ; aperture suborbicular ; outer lip thickened at the 

 margin, and a little spreading. 



EXTINCT SPECIES. 



1. C. pyramidalis. — Pyramidal, with six projecting tuberculated angles; 

 whorls ten or eleven, transversely tricarinated, carinse tuberculated ; six com- 

 pressed tubercles on the upper part of the last whorl ; oviter lip expanded 



(Murex angulatus, Brander, f. 46.) Sower. Min. Conch, t. cxxvii. f. 1 



London Clay. 



2. C. gemijiatum.— Conical, elongated, smooth, with seven or eight longitu- 

 dinally disposed pairs of acute tubercles on each whorl ; whorls about twelve, 

 lip even. Soiver. Min. Conch, t. cxxvii. f. 2 London Clay. 



