212 HELIX-OBBA. 



Section NEOCEPOLIS, Pilsbry. 



Shell striate or granulate ; aperture oblique, the ends of peristome 

 but slightly converging ; umbilicus narrow or closed ; last whorl but 

 little deflexed in front ; columella thickened, usually toothed ; hav- 

 ing sometimes a palatal tooth also. 



Section OBBA, sensu strido. 



Large forms, rudely sculptured with coarse radiating folds or 

 malleations above, obliquely descending or revolving wrinkles or 

 ridges below, the sculpture- ridges not parallel to the lines of growth ; 

 color brown or brownish, banded with lighter. 



A. Last whorl very deeply descending in front ; periphery rounded, 



mamilla. 



B. Last whorl only slightly descending in jront. 



a. Periphery rounded ; inner whorls of spire radiately plicate, 



quoyi. 



b. Periphery acutely keeled. linnseana* 



H. MAMILLA Fe>ussac. PI. 53, figs. 100, 1, 2 ; pi. 40, fig. 95. 



Shell globose-depressed, not carinated, umbilicated, solid, strong, 

 opaque ; yellow, with a broad brown band below the suture, a nar- 

 rower one at the circumference, and a broad one on the base, fading 

 out toward the umbilicus ; spire convex ; last whorl rounded at 

 periphery, very deeply descending in front ; lip broadly reflexed, 

 white. 



A compact, solid shell, with low dome-shaped spire ; surface of 

 the spire-whorls sculptured with strong, coarse, radiating folds ; 

 body-whorl corrugated by close, coarse folds, descending in a direc- 

 tion much more oblique than the growth-striae, the base irregularly 

 pitted and indented. Whorls 5, the inner two smoother, the first 

 whorl smooth, white ; last whorl rounded at periphery, but often 

 encircled by an inconspicuous raised line indicating the position 

 of the carina in the keeled forms of Obba. The whorl is very 

 deeply deflexed in front ; aperture very oblique, irregularly oval, 

 upper and outer margins well arched, baso-columellar margin 

 straightened ; lip broadly reflexed, its face white, thickened, con- 

 vex ; margins approaching, joined by a cord of white callus. Um- 

 bilicus more or less concealed by the reflexed columellar lip. 



Alt. 30, greater diam. 36, lesser 31 mill. 



Alt. 25, greater diam. 30 mill. 



Northern Celebes. 



