CHAPTER LXXV: THE SIPHON SHELLS 



Family SiPHONARiiDyE 



Genus SIPHONARIA, Blainv. 



Shell patelliform, apex sub-central, posterior muscle scar 

 horse-shoe shaped, divided on the right by a deep siphonal groove. 

 Animal with broad two-lobed head; no tentacles; rudimentary 

 branchia^ form triangular folds of the lining membrane of the 

 mantle. Marine mollusks chiefly of the Tropics, living attached 

 to rocks between tide marks, or if higher, where they are dashed 

 occasionally by spray. 



S. gigas, Sby., has a solid, porcellanous shell, polished within 

 and shaded to black at the margin. Exterior dingy, thrown into 

 many sharp-edged plaits, becoming worn with age. Length, 

 2 inches. 



Habitat. — Panama. 



S. alternata, Say, has a backward pointing beak, drawn 

 almost as far from the centre as the margin of the shell. Fine 

 lines sculpture the basal half of the cone. Cblour brown, with 

 radiating lines of white. Base oval. Diameter, -^ inch. 



Habitat. — East Florida. 



296 



