188 ORTHALICUS. 



visible to the naked eye; lip well expanded or 

 reflexed, white or light colored. 



Group of O.fraseri, p. 192. 



d l . Spiral stria? fine and close, the shell rather 

 smooth; lip and entire aperture pure white, 

 the former expanded or reflexed ; columella 

 with a strong fold above. 



Group of 0. deburghicE, p. 196. 

 c 1 . No spiral striation ; peristome colored. 



Group of 0. labeo, p. 199. 



Subgenus ORTHALICUS (restricted). 



The selection of H. sultana Dillw. (gallina- sultana auct.), as typi- 

 cal of Orthalicus by Gray and Troschel, restricts that group to a few 

 large, richly variegated shells inhabiting the Guianas, western Peru 

 and central and northern Bolivia all abundantly watered forest 

 regions. The exact definition of the species and varieties awaits 

 fuller knowledge of their geographic distribution, which in large part 

 still remains'to be mapped. 

 O. SULTANA (Dillwyn). PI. 47, figs. 6, 7, 8. 



Shell large, ovate, with rather short, conic spire and ventricose 

 last whorl ; thin ; immature specimens more or less fragile. Last 

 whorl buff, closely veined with irregular and anastomosing, or fes- 

 tooned purplish or brown stripes, and encircled by three principal 

 blackish-purple or brownish-purple spiral bands irregularly inter- 

 rupted by white or creamy spots or stripes ; narrower or indistinct 

 bands in the intervals between the main ones (a variety with five 

 bands) ; the upper band usually formed of a broad series of large 

 dark alternating with light (or white) blotches; the spire closely 

 marked with festooned stripes and two or three spot-girdles or bands 

 of angulation. Surface lustreless, finely plicatulate obliquely, decus- 

 sated by close spiral striae, at narrow intervals stronger. Whorls 6, 

 moderately convex, the first 2^ forming the densely thimble-punctate 

 obtuse nepionic shell, the earliest two whorls dark brown above ; last 

 whorl very large ; suture not deflexed anteriorly. 



Aperture large, oblique, ovate, bluish white (lilac colored in a 

 variety) and variously mottled within ; peristome thin, unexpanded, 

 light brown (or in a variety, black-brown in adults, with a rather 

 wide internal border of the same color, fading through purple into 



