POLYTROPA. 171 



number of forms to which different names have been attached. 

 These include P. rugoxa, Qnoy (fig. 112), which does not differ 

 much ; P. /r?>^,s-, Dunker (fig. 124), and P. albomarginata, Desh. 

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

 Reeve (fig. 1.22), an extreme ribbed form, together with an inter- 

 mediate state figured by Kiener and Kiister. 



Dr. Gould w:is 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. 

 I figure of these /'. calaracta, Reeve (fig. 132), as of Chemnitz, 

 P. lay en aria, Duclos (fig. 128), P. dubia, Kranss (tig. 127), P. 

 nrrxicnlor. 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. 



fioreal Seas ; North Europe to North Africa (not Mediterranean) ; 



Northern Atlantic Shores of the United States to Greenland ; 



(Siberia to Japan ; Behring^s Straits to California. ?} 



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. 

 kaemattoma, I have considered it preferable to retain some of 



