XKRITI.NA. 45 



I have included in the above description forms heretofore re- 

 garded as distinct, but which do not appear to possess permanent 

 differential characters. The principal mark of this species is the 

 presence of spiral sculpture, but I have before me specimens in 

 which this is partially obsolete, suggesting very strongly a connec- 

 tion with X. dubia. The typical N. cornea embraces the smaller 

 forms, with less developed sculpture, columellar area yellowish, be- 

 coming deeper, orange or blackish on the outer edge, the margin 

 edentulate. Here may be placed as synonyms N. amphibia and X. 

 ampullaria, Lesson, N. morio, Deshayes, A*, xnhatn, A n ton, N. Savesi, 

 Gassies (fig. 1), and X. fjuyrdex, Troschel, with var. utr<unentaria, 

 Tapparone Canefri. 



Var. HUBSULCATA, Sowb. Figs. 98, 1M>. 



The shell is somewhat larger, often more distinctly sculptured, the 

 color patterns more obscure or unicolored, the columellar margin 

 obsoletely denticulated, the area white, with black blotches behind. 



A. subsinuata, Mousson is a synonym, 'being a typographical 

 error for subsulcata. 



Var. CIITMMOI, Keeve. Fig. 100. 



The largest form of the series, with moderate sculpture and 

 darker epidermis, unicolored or obsoletely maculated and dotted ; 

 columellar margin edentulate, area orange-brown. 



Var. XOLANI, Tryon. 



Light violaceous, with several black bands over which are scat- 

 tered opaque white fleckings. 



A single specimen of this exquisite color-variety of the typical 

 N. cornea is in- the collection of the Philadelphia Academy. 



Section THEODOXUS, Montf. 1810. 



X. DANUBIALLS, Miihlf. PI. 15, figs. 2-9. 



Subglobose, occasionally spirally constricted (fig. 7), yellowish 

 white, with irregular purple or brown undulating or zigzag lines, 

 aperture bluish white. Diam. 11-13 mill. 



Lower Danube, Northern Italy, etc. 



The synonyms of the typical form are X. Marsigliana, Hartm., 

 -V. Daitubiensis, Sadler. 



Var. STRAGULATA, Miihlf. Figs. 4, 5. 



Angulate form ; spire depressed, shoulder of whorl obtusely an- 

 gular, strigations wider, sometimes entirely black. The synonyms 



