36 ANCTUS. 



Genus ANCTUS v. Martens, 1860. 



Anctus v. MART, in Albers' Die Hel. (2 edit.), p. 214 (November, 

 I860!), type and sole species u B. anchistomus Wagn. = B. anyio- 



stomus Wagner. Gonyostomus sp., ALBEKS, 1850 Stenostoma sp., 



SPIX 1827 (preoc.). 



Shell ovate-conic, of numerous (7-8) whorls, the last ascending in 

 front, the aperture built forward, forming a wide umbilical area and 

 long rima or umbilical suture. Apex smooth. Aperture over half 

 the shell's length, narrow and parallel-sided, without lamella or 

 folds within ; the peristome narrowly reflexed, thickened within. 

 Soft anatomy unknown. 



The two species known are from the mountains of Bahia province, 

 Brazil. Both are white shells, conspicuously striped with brown 

 and black, and remarkable for their narrow apertures ; the end 

 gained in Odontostomus by the development of tooth-like processes 

 being here attained by a lateral compression or strangling of the 

 whole mouth, as the generic name denotes. 



The color-scheme of stripes (compare 0. inflatus Wagn., dubiosus 

 Jay) and the long umbilical suture, as well as the crowded whorls of 

 the spire, are all features commonly encountered in Odontostomus; 

 and there is every reason to believe that when the scalpel lays bare 

 the internal organization of Anctus, it will prove to resemble closely 

 such species of Odontostomus as dubiosus, angulatus and their allies. 

 The chief difference from Odontostomus is that the apex is smooth ; 

 but still I think that if no more weighty divergence is found in the 

 soft parts, Anctus might advantageously be reduced to a subgenus of 

 Odontostomus. 



A. ANGIOSTOMUS (Wagner). PI. 8, fig. 86. 



Shell ovate-conic, having a long, deep and oblique umbilical 

 rimation, thin but rather strong ; opaque white, striped longitudinally 

 with mingled brown and black narrow stripes, which taper above on 

 the spire, and are often partially interrupted by a light peripheral 

 line. Surface striated. Spire straightly conic, the apex corneous- 

 brown, obtuse, smooth. Whorls 7-j-, slightly convex, the last narrow 

 at the base, the suture ascending in front. Aperture vertical, very 

 narrow and parallel-sided, more than half as long as the shell, light 

 brown inside ; peristome white, narrowly reflexed, evenly thickened 

 within, the outer and columellar margins parallel. 



