124 MALACOZOA. GASTEROPODA. PECTINIBRANCHIATA. 



1. Bythinia tentaculata. Tentaculated Bythinia. 



Shell ovato-conical, with the apex pointed, the turns five or 

 six, pellucid, rather glossy, faintly striated transversely, convex, 

 the last very lai'ge, ventricose; the mouth nearly half the 

 whole length, ovate, angulate behind, with the peristome thin, 

 reflexed on the left side ; the colour yellowish-grey. Length 

 five-twelfths of an inch, breadth rather more than half the 

 length. 



Although very common in England, this species has not 

 been met with in the eastern parts of Scotland. In August, 

 1 842, a single specimen was found by Miss Anne Macgillivray 

 while searching the beach with me, near the mouth of the Dee, 

 and in the beginning of October another specimen by myself 

 in the same place. At the former time there was a profusion 

 of small shells along high water mark, among which we found 

 many marine species, together with specimens of Limnaeus 

 pereger, Limnaeus truncatulus, Clausilia perversa, Ancylusflu- 

 viatilis, and Neritina fluviatilis. Whether these shells may 

 have come from the Dee or Don, or from among ballast in the 

 harbour, or been drifted from a distant coast, can only be con- 

 jectured. 



Helix tentaculata. Linn. Syst. Nat. 1249. — Helix tentaculata. 

 Penn. Brit. Zool. 140. PL 86. f. 140.— Nerita Jaculator. Muller, 

 Venn. Terr, et Fluv. ii. 185. — Helix tentaculata. Mont. Test. Brit. 

 389. — Paludina impura. Lamk. Syst. vi. 2, 175. Ed. n. viii.514. — 

 Paludina tentaculata. Flem. Brit. Anim. 315. 



Family II. — Naticina. 



Animal with the body elongated, spirally rolled into 

 a globose form, and covered with a shell; head flat- 

 tened, semilunar, emarginate ; two long conical tenta- 

 cula, eyes on short pedicels at the outer side of their 

 base or sessile ; orifice of the branchial cavity an oblique 

 slit, without tube or canal; two unequal pectinated 

 branchiae ; orifice of the generative organs near the base 

 of the right tentaculum ; the foot very large, thick, and 

 roundish. A horny or calcareous operculum. 



Shell spiral, globose or ovate, with the aperture large, 

 roundish, semicircular, or ovate, without anterior canal 

 or notch ; the columellar margin straightish, or septi- 

 form. 



