27S MOLLUSC A. PULMONIFERA. Planorbis. 



122. P. albus. — 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. l!) — Helix alba, Mont. Test. Brit. 

 459. Supp. tab. xxv. f. 7 — P. bispidus, Drop. 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. nautilus. — Shell flat above, concave below, with 



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



Turbo Nautilus, Linn. Syst. i. 1241 — P. imbricatus, Mull. Verm. ii. 



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



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



Breadth |th 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, Lightfoot, Phil. Trans. 1786, 165. 



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

 and Scotland. 



Breadth about T e 5 ths 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 ; the shallow central cavity exhibits the preceding whorls ; 

 below, 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 exigua subfusca, List. An. Ang. 145. Conch, t. 138. f. 43. — He- 

 lix vort. Linn. 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 §tbs 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. complanatus. — 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, Drap. 



Moll. 45 In ponds and ditches, common. 



Breadth upwards of half an inch ; whorls 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. 



