358 MOLLUSCA. CERITHIAD^. Potamidum- 
3. Q.funaium — Conical, elongated, with two obtuse crenulated transverse 
ridges upon each whorl ; upper part of each whorl thickened and tuberculated ; 
mouth squarish ; base smooth. Sower. Min. Conch, t. cxxviii. — In Plastic 
Clay. 
4. C. funiculatum — Pyi'amidal ; sides straight ; whorls with four, nearly 
equal, crenulated carinae on each ; base with several plain elevated ridges. 
Sower. Min. Conch, t. cxlvii. f. 1, 2.-— Plastic Clay. 
5. C. intermedium. — Pyramidal, sides straight ; whorls with a largely cre- 
nulated margin, and five or six unequal carinae on each ; base with several 
elevated ridges. Sower. Min. Conch, t. cxlvii. f. 3, 4. — Plastic Clay. 
6. C. duhium. — Turrited ; whorls with a row of compressed tubercles near 
the middle, and two transverse rows of lesser tubercles below ; base with one 
or two rows of tubercles. Sower. Min. Couch, t. cxlvii. f. b...— London Clay. 
7- C. -Turrited, obscurel}^ longitudinally undulated; whorls 
convex, bearing above the middle a large tuberculated carina, below with two 
or three transverse tuberculated carinae ; beak very short. Sower. Min. 
Conch, t. cxlvii. f. 6, 7 ; qnd t. 339. f. 3 . — Plastic Clay. 
8. C. rigidum. — Subulato-conical, nearly smooth ; lower whorls surrounded 
by a keel near their upper parts. (Buccinum. rig. Brander, f. 43.)— Potami- 
dis reg. Sower. Min. Conch, t. 338 — London Clay. 
9. C.concavum , — Subulato-conical; spirally striated ; whorls rather concave 
towards the upper part ; costated ; costae obscure, arched, with a slight emi- 
nence above the middle of each ; base with one or two granulated carinae, 
convex ; lip enlarged below, with a small groove in its upper angle — Pota- 
mides con. Sower. Min. Conch, t. cccxxxix. f. 1, 2. — Upper marine formatimy 
Isle of Wight. 
10. C. margaritaceum. — Conical, turrited, five close rows of bead-like gra- 
nules surround each whorl, the first and fourth rows minute, the fifth larger 
than the other two ; lip expanded, plicated ; pillar recurved, obtusely cari- 
nated. — Potamides marg. Soiver. Min. Conch, t. cccxcix. f. 4. — Upper marine 
formationy Isle of Wight. 
11. C. Subulato-conical, or subcylindrical ; whorls longitudinal- 
ly plaited, transversely sulcated and striated ; sulci three or four ; base con- 
vex ; lip crenulated.— Potamides plic. Sower. Min. Conch, t. cccxl. f. 2. — Up- 
per marine formationy Isle of Wight^ 
12. C. duplex. — Subulato-conical, with two rows of tubercles upon the up- 
per, and three upon the lower whorls ; upper rows of tubercles largest ; sides 
of the whorls flat ; base flat, with two carinae near its edge ; beak short, inner 
edge rising upon the pillar — Potamides duplex, Sower. Min. Conch, t. cccxl. 
f. 3. — Upper marine formationy Isle of Wight. 
Gen. potamidum.— -C anal very short ; aperture entire re- 
trally ; outer-lip patulous. 
1. P. acutum Conical, turrited ; whorls convex, bicarinated ; carinae acute ; 
base convex, bistriated ; aperture orbicular, v/ith a narrow short beak, Sower. 
Min. Conch, t. cccxli. f. 2. — Lower fresh water formationy Isle of Wight. 
2. P. ventricosum Conical, turrited; whorls ventricose, costated, trans- 
versely striated ; striae two or three upon each whorl, most elevated upon the 
costae ; aperture orbicular, with an extremely short beak. — Sower. Min. Conch, 
t. cccxli. f. 1 . — Fresh water formationy Isle of Wight and Cowes. 
