m MOLLUSCA. PULMONIFEEA. Planorbis. 
P, aTbus. — Concave on both sides, striated transversely 
and longitudinally ; aperture oblique, dilated. 
Mull. Verm. ii. 164- — Helix umbilicata quatuor anfractibtis apertura sub- 
rotunda, Walk. Test. Min. 5. tab. 1. 19. — Helix alba, Mont. Test. Brit. 
459. Supp. tab. xxv. f. 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 j 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 weU 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 y^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 carinatecU 
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 |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 Helioe rhombea of Dr Turton, Conch. 
Diet. 47. 
126. 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. Bmp. 
MoU. 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. 
