•278 MOLLUSC A. PULMONIFERA. Planorbis, 



122. P. alhus. — Concave on both sides, striated transversely 



and longitudinally ; aperture oblique, dilated. 



Mull. Verm. ii. 164. — Helix umbilicata quatuor anfractibus apertura sub- 

 rotunda, Walk. Test. Min. 5. tab. 1. ly — Helix alba, Mont. Test. Brit. 



459. Supp. tab. xxv. £ 7 P- hispidus, Drap. Moll. 43. — In ponds, com- 



mon. 



Breadth about a quarter of an inch ; whorls four, last whorl greatly larger 

 than the preceding one, slightly depressed ; aperture entire ; lower-lip join- 

 ing the body, ascending ; the upper-lip advanced. 



123. P. nautibis. — Shell flat above, concave below, with 

 transverse ridges, which, on the margin, form a spinous ridge. 



Turbo Nautilus, Lmn. Syst. i. 1241. — P. imbricatus, 3Iull. Verm. ii. 



165 Helix, Walk. Test. Min. 6. t. i. f. 20, 21.— Turbo Naut. Mrnit. 



Test. Brit. 466. Supp. t. xxv. f. 5 — In ditches in England, common. 



Breadth ith of an inch ; whorls four, flat, but well defined by the separat- 

 ing line ; below, a deep cavity, exhibiting more rounded whorls ; aperture en- 

 tire, suborbicular. As the transverse ridges are partly cuticular, they are 

 liable to be rubbed off. 



124. P. nitidus. — Glossy ; a central cavity on both sides ; 

 aperture interrupted by the preceding whorl. 



Mull. Verm. ii. 163 Helix fontana. Light foot, Phil. Trans. 1786, 165. 



t. 11. f. 1, 4. Mont. Test. Brit. 462. t. vi. f. 6— In ditches, England 

 and Scotland. 

 Breadth about j-fjths of an inch ; nearly equally convex on both sides ; 

 above, the body-whorl is highest on its central edge, sloping downwards to 

 the exterior margin ; tlie shallow central cavity exhibits the preceding whorls ; 

 beloAV, the body-whorl is nearly flat, and the deep central cavity scarcely dis- 

 plays the preceding whorl ; aperture subtriangular, the lips on both sides em- 

 bracing the body-whorl. 



** Whorls carinated- 



125. P. vortex. — Whorls six or seven; slightly concave above; 

 beneath flat. 



Cochlea exigvia subfusca. List. An. Ang. 145. Conch, t. 138. f. 43. — He- 

 lix vort. Li)in. Syst. i. 1243 Planorbis vort. Mull. Verm. ii. 158. — 



H. vort. Penn. Brit. Zool. iv. 133. Mont. Test. Brit. 454. Supp. t. xxv. 



f. 3 In ditches, England and Ireland. 



Breadth |ths of an inch ; whorls increasing gradually, narrow, broadest on 

 the under side ; slightly carinated near the lower edge ; mouth subtriangular. 



In its young state, this seems to be the Helix rhombea of Dr Turton, Conch. 



Diet. 47. 



126. P. coynplanatus. — Whorls five, carinated at the lower 

 edge ; above, nearly concave ; beneath slightly flat. 



Helix comp. Linn. Syst. 1242. — Plan, umbilicatus. Mull. Verm. 160 — 

 H. comp. Mont. Test. Brit. 450. Supp. t. 25. f 3. — P. marginatus, Drajh 



Moll. 45 In ponds and ditches, common. 



Breadth upwards of half an inch ; M'horls increasing so as to form a slight 

 concavity ; rounded ; line of separation deep ; close upon the under margin is 

 the keel, which does not enter the subquadrangular aperture; the whorls be- 

 low slightly rounded ; lines of growth distinct ; tentacula dusky, dark in the 

 middle. 



