HELIX-I3OMERIA. 139 



H. SUBELLIPTICA Moussoii. PI. 46, figs. 28, 29, 30, 



Umbilicated, depressed, thick lens-shaped, striate, not granulate, 

 brownish-corneous ; spire convexly-depressed, regular ; apex nearly 

 flat ; suture impressed-linear. Whorls 4, the first regularly widening. 

 nearly flat, the last whorl obtusely carinated, the circumference 

 elliptical in outline, rather tumid, angulose, briefly descending an- 

 teriorly, constricted at the aperture, more swollen beneath, the side 

 of the umbilicus obtusely impressed, obscurely lineated ; aperture 

 oblique (50 with axis), obtusely, obliquely rectangular; peristome 

 expanded, reflexed, especially at base, margins connected by a callous 

 thread-like at its outer edge, with a minute compressed denticle 

 within ; upper margin curving a little anteriorly, basal margin 

 oblique, nearly straight, sub-thickened, protruding into the umbilicus 

 at the insertion ; umbilicus one-seventh the diameter of shell. 

 (JMouss.} Alt. 13, diam. maj. 38, min. 23 mill. 



Bugua, Amazons. 



H. subelliptica Mouss. in Malak. Blatter, 1869, p. 170. PFEIFFER, 

 Novit. Conchol. iv, p. 117, t. 127, f. 4-6. 



This species belongs to the characteristically South American 

 group Isomeria. and is most nearly allied to H. continua Pfr. It 

 has, however, no trace of granulation, no whitish spots, no acute 

 keel ; its contour is somewhat elliptical, reminding one of If. erronea 

 Albers. Moreover, the umbilicus is quite open, and although 

 perfectly adult the parietal tooth is very small and elongated, and 

 does not at all obstruct the aperture. 



H. ALOAGANA Jousseaume. PL 43, figs. 48, 49. 



Shell umbilicate, orbicular, carinated, more convex above than 

 beneath ; the shell, although thinner than other species of the same 

 group is still very solid ; it is covered with a thin epidermis, very 

 adherent, and granulate, the granulation visible only under a lens; 

 incremental stride finer, closer, more regular on the base than above, 

 irregular, oblique and always stronger as they approach the suture; 

 color brown, a little lighter on the earlier whorls ; the spire is con- 

 vex, rounded, depressed- conoidal, formed of 4J whorls, depressed 

 and angular at the periphery, regularly, moderately rapidly increas- 

 ing ; the first two whorls moderately strong and rugose, form a flat 

 reddish apex; the last is irregular, thickened on its latter portion 

 and less carinated, deflexed toward the aperture, constricted behind 

 the peristome ; aperture brown inside, very oblique, semioval ; 



