POLYTROPA. 171 



number of forms to which different names have been attached. 

 These include P. rugosa, Quoy (fig. 112), which does not differ 

 much ; P. tristis, Dunker (fig. 124), and P. albomarginata, Desh. 

 (fig. 121), which is a depauperate state of tristis ; P. Quoyi, 

 Reeve (fig. 122), an extreme ribbed form, together with an inter- 

 mediate state figured by Kiener and Kiister. 



Dr. Gould was the first (in Moll. Wilkes' Exped.) to notice the 

 variation from costate to smooth forms in the New Zealand 

 specimens, and the latter becomes usual .in those from the Cape. 

 F figure of these P. cataracta, Reeve (fig. 132), as of Chemnitz, 

 P. lagenaria, Duclos (fig. 128), P. duUa, Krauss (fig. 127), P. 

 versicolor, Wood (fig. 133), according to Kiister; the last con- 

 necting with the ribbed form. P. Zeyheri, Krauss, appears to be 

 founded on a young shell. \ 



P. HARPA, Conr. PI. 52, fig. 145. 



Chocolate, the revolving ridges maculate with white ; bluish 

 within, columella and lip-dentations tinged with chocolate, with 

 narrow revolving bands of the same color. Length, 1-1-25 inches. 



Sandwich Isles. 



\ rather constant species in sculpture and coloration, and ap- 

 parently of limited distribution. 



P. LAPILLUS, Linn. 



Shell usually whitish or orange-brown or chocolate-colored ; 

 with sometimes one to several white revolving bands. Obso- 

 letely ribbed, conspicuously ribbed, or covered with revolving 

 striae ; surface smooth, or imbricated or lamellate by the crossing 

 of the growth-lines upon the revolving ribs. Lip at the rest 

 period in the adults usually much thickened within and dentate. 



Length, 1-2-5 inches. 

 Roreal Sens ; North Europe to North Africa (not Mediterranean) ; 



Northern Atlantic Shores of the United States to Greenland ; 



(Siberia to Jn/pan ; Behring's Straits to California, f} 



The quantity and variety of material before me, embracing a 

 rich series of forms from many localities, together with the com- 

 parison of the numerous descriptions and figures that have been 

 published, induce me to include under this, the oldest name, a 

 very large number of nominal species. As in the case of P. 

 hsemastoma, I have considered it preferable to retain some of 



