MALACOZOA. GASTEROrODA. PECTINIBRANCHIATA. 51 



AsiPHONATA. Without a Branchial Tube. 

 Family I. — Paludinina. 



Body elongated, spiral, wdtli a spiral shell ; two coni- 

 cal, elongated tentacula, having the eyes situated at their 

 base externally ; the aperture of the shell oval, with the 

 peristome complete ; a corresponding operculum. The 

 name from the Genus Paludina, 



Genus 1 . Paludina. — Animal with the tentacula taper- 

 ing, of moderate length. SheU oval, with the peristome 

 thin ; operculum horny. Pdlus, a marsh. 



1. Paludina vivipara. — Shell oval, rather thin, with 

 the turns very convex, horn-coloured, with three spiral 

 brown bands. Viinparus, producing live young. 



Genus 2. Bythinia. — Animal with the tentacula slender 

 and elongated. Shell oval, with the peristome thickened 

 internally ; operculum calcareous. Name, I suppose, 

 from (3v$ios, dwelling in the deep. 



1 . Bijthinia tentaciddta. — Shell ovato-conical, of five 

 convex turns ; the mouth nearly half the entire length. 

 TentaculdtuSy having remarkable tentacula. 



Family II. — Naticina. 



Body elongated, spiral, with a spiral shell ; two conical 



tentacula; eyes on short pedicels at the outer side of 



their base ; the aperture of the shell roundish ; a horny 



or calcareous operculum . Name from the Genus Nd tica . 



Genus i. Natica. — Shell ^obose or oval, spiral, um- 

 bilicate ; the aperture roundish or semicircular, with the 

 outer lip thin, the inner partly covering the umbihcus. 

 Ndt^s, a buttock or prominence. Lamarck. 



1 . Ndtica monilifera. — SheU globose, of five very con- 

 vex turns, having a series of purple spots near their 

 upper margin ; spire very short and convex, Monilis, a 

 necklace or string of beads ; fero, to bear. 



2. Ndtica rutila, — Shell subglobose, rather broader 

 than high, of four very convex turns, dull-red, with a 

 white baud margining the narrow canaliculate suture ; 



