72 MALACOZOA. GASTEROPODA. PULMOBRANCHIATA. 



Cirrobranchidta, Blainville. Cirrus, a filament ; 

 branchice, gills. 



Family I. — Dentaliina. 

 Animal much elongated, conical, with a conico-tu- 

 bular shell, open at both ends. Named from the Genus 

 Dentalium. 



Genus 1. Dentalium. — Shell much elongated, conical 

 slightly curved, open at both ends, with the aperture 

 circular. Named from resembling a tooth, dens. Lin- 

 naeus. 



1. Dentalium Entails. — Shell elongated-conical, slight- 

 ly curved, tapering to a fine point, but truncate at the 

 tip, and having a small slit in the margin of its upper 

 aperture, the surface glossy, obsoletely striulate, white. 

 Entalis, perhaps a corruption of Bentalis. 



ORDER I.— GASTEROPODA PULMOBRANCHIATA. 



Respiratory apparatus a pulmonary cavity on the 

 back, on which the vessels form a complex network, 

 and communicating externally by an opening on the 

 margin of the mantle, over the neck, on the right side, 

 capable of being closed at will. 



Although they all respire air, many of them reside 

 habitually in water, but come occasionally to the surface. 

 They all feed on vegetable substances, 



SECTION I.— TERRESTRIA. 



Family I. — Limacina. 



Animal with the body elongated, contractile, becom- 

 ing convex or induplicate, united in its whole length 

 with the foot, and covered anteriorly above with a shield- 

 like mantle ; the head and tentacula retractile into the 



