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BULLETIN 10 0, UNITED STATES NATIONAL MUSEUM 



colored, marked by numerous axial brown fulgurations. which are 

 about as wide as the spaces that separate them; they extend to the 

 peristome on the last whorl. The upper side of all the whorls is 

 strongly rounded, and marked by rather strong incremental threads 

 and closely spaced microscopic spiral striations where protected by 

 the sutures. The whorls show numerous slender fine lines, which 

 here are stronger than those in typical Opisthoporus quadras') from 

 Balabac. The siphon is about 1 mm behind the peristome and is 

 directed forward in a curve. Periphery well rounded. Base openly 

 umbilicated, showing all the whorls within. These whorls are 

 strongly rounded and marked here as on the upper surface, but the 

 sculpture is slightly finer. Aperture and operculum as in Opistho- 

 porus quadrast quadras'/. 



Figure 1. — Operculum of Opisthoporus 



Type.— U.S.N.M. No. 313010, from Iwahig, Palawan. It has 

 4.5 whorls, and measures: Height, 7.5 mm; greater diameter, 1G.2 

 mm; lesser diameter. 11.7 mm. 



Additional material. — Additional specimens examined yield the 

 data sriven in the table below. 



Remarks. — This subspecies differs from typical <> pixtlioporus 

 quadrasi quadrasi in being larger and in having dark early whorls 

 and stronger sculpture. 



