148 MALACOZOA. GASTEROPODA. PECTINIBRANCHIATA. 



There is confusion among the references to this species even 

 in the most recent works. The species above described is very 

 certainly that of Montagu and Fleming ; but Paludina muri- 

 atica of Lamarck, and Cyclostoma acutum of Draparnaud, as 

 well as Turbo ulvse of Pennant, refer to quite a different 

 animal. 



2. Rissoa muridtica. Horn~coloured Rissoa. 



Shell oblongo-turrite, rather thin, transparent, somewhat 

 corneous ; the spire elongated, tapering to a small but bluntish 

 point ; the whorls six, slightly convex, obscurely striated 

 transversely, the last turn rounded, without an angle ; the 

 aperture ovate, acute behind, the peristome thin, considerably 

 reflected on the columellar side, leaving a slight fissure, but 

 concealing the umbilicus ; the colour pale yellowish or green- 

 ish-grey. Length about two-twelfths and a-half, breadth less 

 than half the length. 



Several specimens found by me and my daughter Anne, in 

 August, 1842, on the sands between the Dee and the Don. 

 I have not however met with it alive in the district. 



Turbo ulvte. Penn. Brit. Zool. — Cyclostoma acutum. Drap. 

 Moll. Terr. et. Fluv. 40. PI. 1 . f. 23. — Paludina muriatica. Larnk. 

 Syst. vi. 2, 175 j Ed. 2. viii. 463.— Paludina acuta. Flem. Brit. 

 Aukn. 315. 



3. Rissoa ventricosa. Ventricose Rissoa. 



Shell ovato-turrite, of five or six thin, pellucid, glossy, con- 

 vex volutions, which are distinctly separated, and slightly 

 rugoso-striate ; the aperture more than a third of the whole 

 length, roundish-ovate, little narrowed behind, with the peri- 

 stome thin, the outer lip semicircular, the inner raised, slightly 

 reflexed, with an umbilical groove ; the colour light yellowish- 

 brown. Length two-twelfths of an inch, breadth nearly half 

 the height. 



Somewhat resembling Rissoa ulvae at first sight, but easily 

 distinguishable by its thinness, semitransparency, and rounded 

 volutions. 



Found by me, in June, 1842, among shell sand, on the 

 beach, near Don-Mouth. 



Turbo ventrosus. Mont. Test. Brit. 317. PI. 12. f. 13.— Cingula 

 ventricosa. Flem. Brit. Anhn. 307. — Pyramis ventrosus. Brown, 

 Illustr. PI. 51. f. 27, 59. 



