.Yl MALACOZOA. GASTEROPODA. PECTIMBRANCHIATA. 



the spire very short and convex ; umbilicus transversely 

 sulcate. Rutihis, reddish. 



3. Ndtica Alderi, — Shell subglobose, of five very con- 

 vex turns, having five series of red spots ; spire very 

 short and rather acute, umbilicus longitudinally striated. 

 Named after Mr. Alder, an English naturalist. 



4. Ndtica nitida. — Shell ovato-globose, of five very 

 convex turns, white without spots ; spire very short and 

 rather acute, umbilicus longitudinally striated. Nitidus, 

 shining. 



5. Ndtica helicbides. — Shell ovate, thin, with a deli- 

 cate epidermis, of five turns, separated by a canali- 

 culate suture ; spire short, convex, rather obtuse, mouth 

 ovate, continuous. Helicoides, a spurious compound 

 of Helix, a snail, and ildos, aspect, appearance, like- 

 ness. 



6. Ndtica squdlida, — Shell subglobose, rather thick, 

 of three and a-half turns, separated by a canaliculate 

 suture ; spire depressed, obtuse ; mouth ovate, conti- 

 nuous. Squdlidits, slovenly or ill-favoured. 



Genus 2. Neritina. — Shell semiglobose or oblong, 

 with the spire very small, the aperture oblique, reduced 

 to a hemispherical form by the thickening of the colu- 

 mella, which shelves to a thin edge. Name altered 

 from Nerita, for a portion of that genus. Lamarck. 



1. Neritina fluvidtilis. — Shell transversely oblongo- 

 elliptical, convex, rather thick, banded, tesselated, or 

 spotted with olivaceous and white. Fluvidtilis, living 

 in rivers. 



Family III. — Turbinina. 



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

 cal tentacula ; eyes on prominences at their base ex- 

 ternally ; mouth with a spiral lingual filament ; shell 

 globose, ovate, conical, or turrite, with the aperture 

 round, subangulate, ovate, or oblong, anteriorly rounded, 

 without notch. Name from the genus Turbo. 



Genus 1. Trochus. — Shell conical, with the spire 

 moderately elevated or low, the aperture somewhat square 



