CEEiTHiujvr: MOLLUSCA. CERITHIADiE. S57 
Trans, vii. II 7 . t. xi. f. 2 — Murex def. Sower. Min. Conch, t. ccccxi. f. 1 — 
In London Clay. 
8. T. sexdentatm. — Ovate acuminated, costated, longitudinally striated, 
transversely carinated ; whorls convex ; aperture elongated, with five or six 
teeth within its outer lip — Murex sex. Sower. Min. Conch, t. ccccxi. f. 3-* — 
Marine formation^ Colwell Bay, Isle of Wight. 
CERITHTADJ',. 
a. Marine. 
Cerithium. 
(Strutheolaria.) 
aa. 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. Bon. 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 lip 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. 7 — Found by Mr Laskey on the 
shores of Nun’s Island, Iona. 
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, carinae tuberculated ; six com- 
pressed tubercles on the upper part of the last whorl ; outer lip expanded 
(Murex angulatus, Brander, f. 46.) Sower. Min. Conch, t. cxxvii. f. 1.— 
London Clay. 
2. C. Conical, elongated, smooth, with seven or eight longitu- 
dinally disposed pairs of acute tubercles on each whorl ; whorls about twelve, 
lip even. Sower. Min. Conch, t. cxxvii. f. 2. — London Clay. 
