280 MOLLUSCA. PULMONIFERA. Segmentina, 



Gen. XXXIV. ANCYLUS.— Shell conical; foot short ; tenta- 

 cula short, flat, and a little truncated. 



129- A.jluviatilis. — Aperture suborbicular ; apex lateral. 



Patella fluviatilis, List. An. Ang. 151. Conch. 1. 141, f. 39. — P. lacustris, 

 Linn. Svst. i. 1260,— An. fluv. Mull. Verm. ii. 201.— P. fluv. Mont. 



Test. Brit. 482. Don. Brit. Shells, t. 147 On stones in rivulets, 



common. 



Length about fths, breadth fths of an inch ; height nearly equal to the 

 breadth ; horn-coloured, with concentric wrinkles crossed by faint lines ; apex 

 pointed, a little recurved. 



130. A. lacustris. — Aperture oblong ; apex nearly central. 



Mull. Verm. 199 — Patella oblonga, Light. Phil. Trans. 1786, 168. t. 111. 

 f. I, 6 — P. lac. Mont. Test. Brit. 484. Don. Brit. Sh. t. 150 — On 

 plants in ditches and lakes. 



Length ith of an inch ; breadth |th, height scarcely y^th of an inch, thin* 

 smooth, greenish, compressed; apex low, pointed, recurved. 



EXTINCT SPECIES. 



1. A. elegans. — Convex, subconical ; aperture longitudinally obovate ; apex 

 oblique, eccentric, near the narrowest part of the aperture — Sower. Min. 



Conch, t. 533 Found in dark-grey sand of the London clay, at Hordwell, by 



Charles Lyell, Esq. jun. 



