GASTEROPODA. 105 
Figures 119, 119 a, two views of the shell. 
CycLosTroMA DIATRETUM (Gould). 
Testa planorboidea, albido-cornea, supra costis acutis remotis, ad inter- 
vallos cincinné clathratis, cincta, laté umbilicata: spira planulata, 
anfractibus quatuor cylindraceis, cito crescentibus, propé suturam 
decliventibus: apertura circularis ; peristomate simplici. 
Cyclostoma diatretum, GouLp; Proceed. Boston Soc. Nat. TELS ing Mle 
205. March 1847. Expedition Shells, 38. 
Suett discoidal, whitish, or pale horn-colour, solid; whorls four, 
rapidly enlarging, forming a flat spire, and sloping downwards to the 
suture; they are cylindrical, but the surface is made angular above 
by four smooth, distant, triangular ribs, and has the intervening con- 
cave spaces most delicately barred by the lines of growth: beneath 
concave, widely and loosely umbilicate, and striated with numerous 
revolving, raised lines. Aperture large, circular, very oblique, barely 
united to the preceding whorl; lip simple. 
Length one-fifth of an inch ; breadth two-fifths of an inch. 
Found at Sandalwood Bay, Feejee Islands. Drayton. 
Answers very nearly to the description of C. orbella, Lam. The 
whorls increase more rapidly, the cost are more distant above, and 
the umbilicus is less broad and open. 
Figures 124, 124 a, 124.0, three views of the shell. 
CyYcLosToMA ROSEUM (Gould). 
Testa parva, solida, elevato-conica, glabra, pallidé rosea: spira acuta ; 
anfractibus sex convexiusculis, supra arcté tabulatis ; sutura bené im- 
pressd: apertura spiram haud equans, ovata; peristomate everso, 
acuto ; fissura umbilical costa circumambiente finita. 
27 
