MALACOZOA. GASTEROPODA. PECTINIBRANCHIATA. 123 



Shell ovato-conical or subglobose, spiral, covered with 

 a thin epidermis ; the turns convex, rapidly enlarging, 

 the last ventricose ; the aperture roundish-oval, angular 

 behind, with the peristome complete, thin-edged, reflexed 

 on the columella. Operculum thin and horny, with, 

 concentric striae. 



1. Paludina vivipara* Viviparous Marsh-Shell. 



Shell thin, ovate-conical, with the apex pointed, the turns 

 five, thin, very convex, transversely striated; the last turn 

 very large, olivaceous with three brown bands, two of which 

 are apparent on the other turns ; the suture deeply impressed ; 

 the aperture roundish-ovate, the inner lip nearly covering the 

 umbilicus. Length about an inch and a fourth, breadth nearly 

 an inch. 



A dead shell was found on the beach near the mouth of the 

 Dee, in the spring of 1842, by Mr. Alexander Cruickshank; 

 another by Mr. Martin, at Torrie. The species has not been 

 found alive in the district Its occurrence on our coasts in- 

 dicates the source whence probably are derived the shells of 

 Bythinia tentaculata, Littorina muriatica, and Neritrina flu- 

 viatilis, sometimes cast on the beaches. 



Helix vivipara. Linn. Fauna. Suec. 529. Cochlea maxima, fusca 

 eive nigricans, fasciata. Lister, Anim. AngL 133. PL 2. f.-18. 

 Cyclostoma viviparum. Drap. MolL Terr, et Fluv. 34. PI. 1. f. 16, 

 17. Paludina vivipara. Lamk.Syst.vL 173. Paludina vivipara. 

 Flem. Brit. Aniin. Paludina vivipara. Gray's Turton, 90. PL 18- 

 f. 118. 



GENUS 2. BYTHINIA. 



Animal elongated, spiral; with the head proboscidifonn; 

 two contractile, tapering, setaceous tentacula, bearing the 

 eyes on prominences at their base externally ; the mouth 

 with a small hispid lingual mass ; the foot oval, with 

 a marginal groove at the anterior part. 



Shell ovato-conical, spiral, covered with a thin epider- 

 mis ; the whorls convex, rapidly enlarging, the last about 

 as long as the spire ; the aperture oval, angular behind, 

 with the peristome complete, thin-edged, reflexed on the 

 columella. Operculum somewhat calcareous, with con- 

 centric stride. 



