Neretina. mollusc. PECTINIBRANCHIA. 321 



4. N. patula Hemispherical, smooth, spire small, depressed ; pillar cavi- 



ty open, containing a spiral ridge. — Sower. Min. Conch, t. ccclxxiii. three lower 

 ^gxxres.— Suffolk Crag. 



5. N. striata Subhemispheroidal, smooth ; spire small, depressed ; pillar 



cavity open ; base concentrically sividXei..— Sower. 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. — Sower. Min. Conch, t. cccclxxix. f. 1. 

 —Suffolk Crag. 



7. N. kemiclausa. — Subglobose ; spire small, conical, pointed ; cavity half 

 closed by the upper part of the pillar lip ; aperture oval. — Sower. Min. Conch. 

 t. cccclxxix. f. 2. — Crag. 



8. N. sigaratina — Much depressed ; pillar cavity large, filled with a lenti- 

 cular callus — Sower. Min. Conch, t. cccclxxix. f. ^.—Lmidon Clay. 



Gen. LIX. NERETINA.— Pillar lip broad, flat, entire ; outer 

 lip patulous. 



280. N.Jiiiviatilis. — Transversely oval, outer Up thin. 



Nerita fluviatilis. List. An. Ang. 136. t. ii. f. 20. Conch, t. 607. f- 43 



Linn. Syst. 1253. Ment. Test. Brit. 470. — On stones in slow running 

 rivers in England and Ireland. 

 Length fths of an inch, breadth fths ; variously streaked or spotted with 



f)urple white and brown ; the whorls rounded, the upper ones small ; slight- 

 y striated across by the lines of growth ; pillar lip white ; lid yellow, with 

 a lateral tooth behind, imbedded in the foot. 



EXTINCT SPECIES. 



1. N. concava. — 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 London Clay to the Crag. 



2. N. uniplicata. — Subglobose, with a concealed spire, and one plait upon 

 the rather convex pillar lip — Sower. Min. Conch, t. ccclxxxv. f. 9. 10. — LoU' 

 don Clay. 



TROCHUSID^. 



Gen. LX. TROCHUS. — Base flat or concave; aperture 

 transversely depressed. 



* Pillar perfo7-ated. 



281. T. Magns. — 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. V 



