Neeetina. mollusc. PECTINIBBANCHIA. S21 
4. N. joaMa— Hemispherical, smooth, spire small, depressed ; pillar cavi- 
ty open, containing a spiral ridge. — Sower. Min. Conch, t. ccclxxiii. three lower 
^gvoces.’^Suffolk Crag. 
5. N. striata. — Subhemispheroidal, smooth ; spire small, depressed ; pillar 
cavity open ; base concentrically striated.— Min. Conch, t. ccclxxiii. 
two upper figures. — London Clay. 
6. N. cirriformis — Globose ; whorls slightly compressed laterally ; spire 
conspicuous ; pillar cavity large, deep, open ; pillar lip thick, with a sinus in 
the middle; aperture small, oblong.— .Soww. Min. Conch, t. cccclxxix. f. 1. 
•^-Suffolk Crag. 
7 . N. hemiclausa. — Subglobose ; spire small, conical, pointed ; cavity half 
closed by the upper part of the pillar lip ; aperture oval.— Min. Conch, 
t. cccclxxix. f. 2. — Crag. 
8. N. sigaratina. — Much depressed ; pillar cavity large, filled with a lenti- 
cular caUus — Sower. Min. Conch, t. cccclxxix. f. %~-^Lmdon Clay. 
Gen, LIX. NERETINA. — Pillar lip broad^ flat, entire ; outer 
lip patulous. 
S80. ~N.Jiuviatilis . — Transversely oval, outer lip thin. 
Nerita fluviatilis. List. An. Ang. 136. t. ii. f. 20. Conch, t. 607* f. 43— 
Linn. Syst. 1253. Mont. Test. Brit. 470. — On stones in slow running 
rivers in England and Ireland. 
Length |ths of an inch, breadth |ths ; variously streaked or spotted with 
purple white and brown ; the whorls rounded, the upper ones small ; slight- 
ly striated across by the lines of growth ; pillar lip white ; lid yellow, with 
% lateral tooth behind, imbedded in the foot. 
EXTINCT SPECIES. 
1. N. concave.— Obovate, with a prominent obtuse spire ; upper part of 
each whorl concave ; aperture semicircular ; lip entire.— Sower. Min. Conch, 
t. ccclxxxv. f. 1-8 — In various strata from the Londm Clay to the Crag. 
2. N. wwijo/icato.-— Subglobose, v/ith a concealed spire, and one plait upon 
the rather convex pillar lip — Sower. Min. Conch, t. ccclxxxv. f. 9. IQ.—Lm~ 
don Clay. 
TROCHUSIDiE. 
Gen. lx. TROCHUS.— Base flat or concave ; aperture 
transversely depressed. 
* Pillar ^perforated. 
281. T. Magus . — Spire subdepressed ; whorls six, flattened 
above towards the deep separating line ; the last whorls tuber- 
culated. 
T. planior, List. Conch, t. 641. 31,— T. Magus, Linn. Syst. i. 1228, 
Mont. Test. Brit. 283— In deep water, not common. 
VOL. I. 
X 
