52 MALACOZOA. GASTEROPODA. PECTINIBRANCHIATA. 



the spire very short and convex ; umbilicus transversely 

 sulcate. Rutilm, 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. Nltidus, 

 shining. 



5. Ndtica helicoides. 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 eZSos-, 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. Squdlidus, 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. Neritma fiuvidtilis. Shell transversely oblongo- 

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

 spotted with olivaceous and white. Fluviatilis, living 

 in rivers. 



FAMILT 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 



