MALACOZOA. GASTEROPODA. PECTINIBRANCHIATA. 51 



ASIPHONATA. Without a Branchial Tube. 

 FAMILY I. PALUDININA. 



Body elongated, spiral, with 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. Shell 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. Fiviparus, 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 pvdlos, dwelling in the deep, 



1 . Bythinia tentaculdta* Shell ovato-conical, of five 

 convex turns ; the mouth nearly half the entire length. 

 Tentaculatus, 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 Ndtica. 



GENUS 1 . NATICA. Shell globose or oval, spiral, um- 

 bilicate ; the aperture roundish or semicircular, with the 

 outer lip thin, the inner partly covering the umbilicus. 

 Nates, a buttock or prominence. Lamarck. 



1 . Ndtica monilifera. Shell 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 band margining the narrow canaliculate suture ; 



