232 LEUCOCHROA. 



Genus LEUCOCHROA Beck, 1837. 



Leucochroa B., Index Moll., p. 16, in part (keeled Xerophila, etc., 

 with L. cariosa, cariosula, candidissima). MORCH, Cat. Yoldi, p. 5, 

 1852, Mai. Bl. iv, p. 109. KoBELT,Nachrbl. 1875, p. 37 ; Iconogr. 

 Land- u. Siisswasser-Moll. n. ser., iii, p. 29. Cakarina MOQ. 

 TAND., MOm. Ac. Toulouse, iv, 1848, and Moll. Fr. ii, p. 69 (not 

 Calcarina d'Orb.). 



Shell solid and strong, chalky, white, subglobose or depressed, and 

 keeled, at least when young ; axis hollow, often closed in the adult ; 

 surface smoothish or pitted; embryonal shell consisting of about H 

 smooth whorls ; last whorl generally deflexed in front. Aperture 

 small, half-round, oblique ; lip blunt and simple (in section Sphinc- 

 terochila much contracted) the columellar insertion dilated, ends re- 

 mote. Type L. candidissima, pi. 56, fig. 13 (see also pi. 56, figs. 

 14, 15, L. cariosa). 



Animal with rather small foot ; upper surface coarsely granular, 

 with a pair of dorsal grooves ; facial grooves indistinct ; no foot 

 margin, caudal pore or longitudinal line on the tail. Sole distinctly 

 tripartite, the middle area wide, side areas narrow, meeting at tail. 

 Mantle-edge rather thick, with very rudimentary right and left 

 body lappets. Right eye retractor passing to the left of the genitalia, 

 not between its branches. 



Jaw (pi. 36, fig. 14, L. candidissima) solid, arcuate, with a low 

 median projection, its surface entirely smooth. 



Radula of the type usual in Helicidce. Middle tooth with square 

 basal plate shorter than the large mesocone ; side cusps absent. 

 Lateral teeth similar but asymmetrical. Marginals with shorter 

 basal plate, the inner cusp (ento- plus mesocone) bifid, ectocone 

 small, simple or bifid (pi. 36, fig. 13, L. candidissima. PI. 36, fig. 

 16, L. boissieri). 



Genitalia (pi. 36, fig. 15, L. bwtica ; pi. 57, figs. 52, 53, L. candi- 

 dissima) : penis very short, narrowing into a much twisted epiphal- 

 lus, upon which below, the retractor muscle is inserted ; terminat- 

 ing in a flagellum and vas defereus. Vagina stout, bearing a 

 flattened spiral, or an elongated gland upon a slender short duct; 

 spermatheca duct long, its lower half convoluted upon the base of 

 the uterus, to which it is closely bound ; bearing a short stouter 

 diverticulum, the end of which is sunken in the uterus ; upper por- 

 tion of the spermatheca duct slender, straight, bound to the uterus 



