100 MOLLUSCA. 
Helicina trochlea, Goutp ; Proceed. Boston Soc. Nat. Hist., ii. 202. 
March 1847. Expedition Shells, 36. 
SHELL minute, depressed, conical beneath, convex, smooth, and of 
a citron colour, somewhat radiately flamed with light and dark ; 
above ashy-gray, and girdled with sharp, elevated ribs, of which there 
are three on the upper and five on the outer whorl, the two last form- 
ing a bicarinated periphery. ‘The interspaces are roundly excavated, 
and barred by elevated lines of growth. ‘There are four whorls, form- 
ing a low, acute, pyramidal spire. The aperture is rather large, of a 
somewhat triangular form, with the lip most delicately reflected. The 
columella projects a little, and is joined by the lip at an angle, and the 
base is coated by a well-marked callus. 
Axis three-fortieths of an inch; base one-eighth of an inch. 
Inbabits Metia or Aurora Island, under stones. Couthouy. 
It has the size and nearly the form of H. rupestris, Pfeiffer, and is 
distinct from all other species by its well-marked, sharp, revolving 
ribs. 
Figures 109, 109 a, 109 6, three views of the shell, enlarged; 109 c, 
natural size. 
HELICINA MULTICOLOR (Gould). 
Testa parva, solidula, conico-globosa, tenuissimé striata, citrina, tn- 
terdum fusco-fasciata, vel omnino fusco-rubra, subtus convexa: spira 
anfractibus quatuor convexiusculis, ultimo ad peripheriam rotundato ; 
sutura impress: apertura lunata, lata ; peristomate simplici, acuto, 
ad basim obtuse angulato ; columella callo copioso induta. 
Helicina multicolor, GouLp ; Proceed. Boston Soc. Nat. Hist., 11. 202. 
March 1847. Expedition Shells, 36. 
ANIMAL cream colour, sometimes spotted with brown. 
SHELL minute, rather solid, globose-conical, delicately striated with 
