T2 CLASSIFICATION. 



SYSTEMATIC. 



CLASS GASTEROPODA. 



Head distinct, furnished with eyes* and tentacles. Body usually 

 protected Toy a spiral or conical univalve shell. Lower surface 

 of body developing a thickened, expanded, creeping disk or 

 foot. 



ORDER I. PROSOBRANCHIATA. 



Animal, creeping or swimming, protected by a shell usually 

 large enough to contain it. Breathing organs (branchiae), plume- 

 like, situated in advance of the heart. Sexes distinct. 



(Section A. SIPHONOSTOMATA.) Animal with its mantle margin 

 prolonged into a siphon conveying the water into the branchial 

 chamber. Carnivorous. Marine. The shell is spiral, the axis 

 usually im perforate, the aperture prolonged into a canal, or 

 simply notched below. Operculum lamellar, horny. 



(Section B. HOLOSTOMATA.) Respiratory siphon wanting, or 

 represented by a mere lobe in the collar of the mantle. Shell 

 spiral or limpet-shaped, generally globular or pyramidal, with 

 the aperture entire below, mid rounded. Marine, fluviatile or 

 terrestrial. Phytophagous usually. (Natica is carnivorous.) 

 Operculum spiral, horny or calcareous. 



SIPHONOSTOMATA. 



Family MURICJ.UJE. Shell spiral, fusiform ; aperture more or 



less canaliculate, or simply notched in front. 

 Sub-family Muricinse. Shell canaliculate ; whorls crossed by 



varices. Operculum ovate. Nucleus subapical. 

 Sub-family Purpurinse. Shell with very short canal, or simply 



notched in front ; but frequently ribbed or nodulous ; colu- 



mella usually broad and flattened ; operculum oblong, nucleus 



elongate, forming the long outer edge. 



The above division into two sub-families holds good as to a 

 majority of the species, but does not cover them all. Thus, 



