148 HELCIONISCUS. 



layer of the interior. The centrum is not sharply defined, generally 

 scarcely darker than the circumference. (Krauss.} 



Compare P. rota Gmel. 



The following variations are described by Krauss : 



VsLY.fasciata (fig. 18). Shell whitish, spotted with brown, painted 

 with six broad blackish-brown bands. The typical form is irreg- 

 ularly and interruptedly striated and flecked, but this has broad 

 bands. 



Var. radiata (fig. 19). The usually somewhat stronger riblets are 

 white, and the smaller riblets and grooves are brown or blackish- 

 brown. Under a lens young examples are seen to be sprinkled with 

 little light-blue flecks. The centrum is yellowish. 



Var. concolor. Shell unicolored, blackish-ashen or tawny. Always 

 smaller, totally unicolored. Centrum whitish. 



H. DUNKERI Krauss. PI. 16, figs. 11, 12, 13, 14. 



Shell small, ovate, convex, very thin ; subpellucid ; whitish or 

 dull yellowish, having 11 radiating black bands and reddish striae, 

 sometimes painted with rose and spots of bluish-green ; radiately 

 striated, the striae fine, subequal ; vertex acute, inclined forward, 

 situated at the front fourth ; margin very finely denticulated, not 

 gaping. Interior shining, colored like the outside, the center 

 yellowish or ashen-whitish. (-fiTr.) 



Length 17, breadth 11, alt. 4f mill. 



Natal. 



P. dunkeri KR., Die Siidafric. Moll. p. 55, t. 3, f. 14. REEVE, 

 Conch. Icon. f. 124. PHIL., Abbild. t. 2, f. 9. 



The thinnest of the South African species. It is somewhat inter- 

 mediate between P. variabilis and P. pruinosa, according to Krauss. 

 Compare also P. compressa young, and P. araneosa Rve. 



H. EUCOSMIA Pilsbry. PI. 71, figs. 61, 62, 63, 64. 



Shell oval, conical, the distance in front of the apex contained 

 from 2| to 3 times in the length of the shell. Posterior slope some- 

 what convex. Sculptured with fine closely granulous radiating 

 riblets, of which every fourth one is usually somewhat larger. Out- 

 side gray-white, spotted all over and indistinctly rayed with rusty- 

 brown. 



Interior yellowish, conspicuously blotched, spotted and rayed with 

 purple-brown or black-brown; the rays being usually 11 or 12 

 in number, either wide or narrow, and spotted with light. The cen- 



