356 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



well-incised, wavy, spiral striations. The aperture is oval with the 

 peristome very strongly developed, expanded, thickened, and re- 

 flected, covering half of the umbilicus. 



The type and eight specimens were collected by Pedro de Mesa at 

 Tara, Abra de Hog, northern Mindoro, Philippine Islands. 



Type.— The type, U.S.N.M. No. 382700, has 4.9 whorls, and 

 measures: Altitude 17.7 mm; greater diameter, 28.9 mm; lesser 

 diameter, 23.3 mm. 



Remarks. — The other eight specimens yield the following measure- 

 ments: 



1 Type. 



The present race can at once be distinguished from Obba sarcochroa 

 sarcochroa Mollendorff by the smaller size and much flatter shape. 



OBBA MESAI, new species 



Shell lenticular, umbilicated, pale buff or flesh-colored, with the 

 upper surface marbled and variegated with brown; the lower surface 

 with an interrupted band of brown at some little distance anterior to 

 the periphery. Peristome white or pale buff. Basal lip provided 

 with a poorly developed median tooth. Periphery of last whorl 

 obsoletely angled. The upper surface behind aperture is marked, in 

 addition to incremental and fine spiral lines, by two sets of very 

 regular microscopic incised lines, which are at right angles to each 

 other and which cut the lines of growth obliquely. I shall call these 

 crisscross lines in the key to the subspecies. 



This species differs from Obba listeri in having the periphery scarcely 

 at all angulated, a character usually very pronounced in that species. 

 In the inflation and rounding of the periphery it resembles Obba 

 planulata more closely, from which the conspicuous interrupted basal 

 band will at once distinguish it. 



The races recognized here are from the islands of Lubang, Ilin, and 

 probably southern Mindoro. 



