History of British animals - University of Guam Marine Laboratory

Segmentina. MOLLUSCA. PULMONIFERA. 279— 127. P. carinatus. — Whorls four ;keel near the middle of thewhorl, and enteringthe aperture. /Cochlea fusca, List. An. Ang. 145. Conch, t. 138. f. 42.— Helix Planorbis,Linn. Syst.i. 1242.— P. car. Mull. Verm. ii. 157-—H. car. Mont.Test. Brit. 451. Supp. t. xxv. £ 1—In ditches.This shell chiefly differs from the preceding,in the whorls above increasingmore rapidly, forming a larger central cavity ; in the greater flatness below ;in the ridge entering the aperture ;and in the tentacula being pellucid yellow.EXTINCT SPECIES.1. P. ajlindricus.— Cylindrical; left side concentrically — striated ;volutionsthree or four, adpressed ;aperture oblong, quadrangular. Sower. Min. Conch,t. 140. f. 2.— Fresh-water formation, Isle of Wight.2. P. obtusus.— Depressed;left side most concave ; volutions embracing^slightly compressed on the right ; aperture obliquely and obtusely obcordate*—Sower. Min. Conch, t. 140. f. 3. Isle of Wight.3. P. lens Lenticular, subcarinated volutions ; embracing; aperture veryoblique, obcordate Sower. Min. Conch, t. 140. f. 4. Isle of Wight.4. P. hemestoma Depressed, smooth ; right side convex, umbilicate ;leftside flat; aperture oblique, sub triangular.— Soioer. Min. Conch, t. 140. f. C.Plastic-clay, Plumstead.5. P. radiatus Lenticular, radiated ;left side umbilicate ; volutions nearlyconcealed ; aperture obcordate. — Sower. Min. Conch, t. 140. f. 5. Greensand,6. P. euomphalus.~—Depressed, subcarinated ; concentrically striated ; rightside flat; left side hvrgely umbilicate; aperture subtriangular. — Sower. Min.Conch, t. 140. f. 1, 9. Isle of Wight—The P. rotundatus of Brongniartismentioned in the Mineral Conchology as occurring in Hordwell Cliff, alongwith Limnea columellaris, t. 528. The three last species are probably marine,and belong to the genus Skenea.Gen. XXXIII. SEGMENTING—Shelldivided internallyby transverse partitions, into several chambers, which communicatewith each other by triradiated apertures.128. S. lineaia,— Shell convex above, flat beneath, with acentral cavity on both sides.Helix lineata dorso convexo umbilicata margine acuto, Walk. Test. Min.8. t. l.f. 28 Nautilus lacustris, Lighffoot, Phil. Trans. 1786, 160. t. 1.f. 1, 7. Mont. Test. Brit. 191. t. vi. f. 3—On aquatic plants in ditches,England.Breadth scarcely a quarter of an inch, glossy, horn-coloured, with a whitishspiral line at the junction of the whorls above ;whorls below, flat, with anacute margin ; aperture obliquely semioval, the lips clasping the body chambersdistant, three in the body-whorl ; partitions of three subtriangular dis-;tinct plates, two lateral and one on the central side ;these partitions formwhite centroperipheral lines externally.