226 HELIX-OBBA. 



feebly sculptured, the carina distinctly wavy; tooth of the basal lip 

 very weak or obsolete ; shell bandless (or bands very faint), or with 

 only a narrow basal band. 



Hidalgo found on the Visayas isles a small mutation having the 

 spire flattened, last whorl very convex beneath. Specimens are be- 

 fore me, but they seem to grade into the typical form. 

 H. BULACANENSIS Hidalgo. PI. 65, figs. 78, 79. 



Shell umbilicated, orbicular, rather solid, not shining, flat above, 

 the base swollen, periphery acutely carinated, sculptured with close, 

 suboblique irregular wrinkles (here and there transversely striated 

 under a lens) ; pale fulvous, brown at the carina, ornamented with 

 a broad whitish zone around the umbilicus ; suture simple. Whorls 

 4-42, flat, the first smooth, the last deeply deflexed in front, sub- 

 constricted beneath. Umbilicus broad, perspective, whitish. Aper- 

 ture transversely lanceolate ; peristome whitish, expanded above, 

 basal margin regularly arcuate, reflexed, margins converging, joined 

 by a narrow, slightly elevated callus. (Hid.) 



Alt. 10, greater diam. 32, lesser 27 mill. 



Province of Bulacan, Luzon, Philippines. 



H. bulacanensis HID., Journ. de Conchyl. 1888, p. 310 ; /. c. 1889, 

 p. 299, t. 13, f. 2. 



Very distinct in form and sculpture. It may group elsewhere 

 than with rota, for the basal lip is toothless. 



3. Group of H. marginata. 



These shells have no trace of a tooth on the basal lip ; the aper- 

 ture is white, with bands inside. Surface very finely obliquely 

 striated, and with either microscopic spiral lines or an excessively 

 minute, dense granulation. Spiral bands 2 to 5. There is no gib- 

 bous ridge behind the upper lip. H. marginata and H. bigonia 

 have a dark streak on the antepenultimate whorl. 



H. BIGONIA Ferussac. PL 55, figs. 45, 46, 47. 



Shell umbilicated, low-conoidal above, flattened below ; white, 

 with one or two brown bands above, one beneath ; surface nearly 

 smooth, having delicate growth-strise and microscopic spiral incised 

 lines. Upper whorls with a purple streak ; basal lip without trace 

 of a tooth. 



The shell is rather elevated, and is angulated at the periphery, 

 the angle sometimes obsolete. There is (typically) a single dark 



