FAMILY PURPURID^ — PURPURA. 135 



GENUS PURPURA. Achmson. 



Animal with a large head. Trunk short or obsolete. Tentacles two, generally in front and 

 approximated, conical, and with the eyes on an inflated portion near the middle, and 

 external. Mouth beneath, almost always concealed by the foot. Foot moderately large, 

 advanced and bilobed in front. Mantle forming a distinct siphon in front. Gills in two 

 unequal series. Orifice of the oviduct at the entrance of the branchial cavity ; that of the 

 vas deferens on the right side of the neck, at the end of the male organ, which is generally 

 voluminous. Vent on the same side. Marine. Shell, ovate, thick, smooth, tubular or 

 angular : spire short ; aperture dilated, emarginale at the base, having a subcanaliculate 

 oblique sinus. Columella depressed, ending in a point. 



Purpura lapillus. 



PLATE Vm. FIG. 175. 



(STATE COLLECTION.) 



Buccinum tapillus. LiN. Gmel. Syst. Nat. 1202. Lam. An. sans vert. Ed. prior» Vol. 7, p. 2H. 

 Purpura id. RussEL, Ess. Journ. Nat. Hist. Vol. 1, p, 69. 

 P. id. Adams, Bost. Journ. Nat. Hist. Vol. 2, p. 268. 



P. id. Gould, Invcrtebrata of Ma.ss. p. 301. 



Description. Shell ovate, thick and solid : spire short and very acute ; suture impressed. 

 Whorls five, with deep revolving furrows and intervening ribs, giving frequently a strong 

 carination to the whorls, which have moreover numerous slight transverse wrinkles. Aperture 

 ovate : lip arched and subacute, with obscure revolving ridges within the margin. Pillar-lip 

 produced, concave externally at the base ; canal short. Opercle horny, oval. 



Color. Varying from white to lemon and orange yellow ; aperture reddish brown within. 



Length, 0-6 -0-8. 



This shell occurs along our coast, from Cape Cod to Florida. It is usually described as 

 varying very much in its markings, constituting strongly marked varieties, which have been 

 considered by others as distinct species. Among these are the two following. 



