532 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



the succeeding marked by lines of growth, which gradually become 

 intensified on the remaining whorls until they reach the strength of the 

 postnuclear sculpture. The later turns are also marked by micro- 

 scopic fine spiral striations. The postnuclear whorls are inflated and 

 moderately rounded, appressed at the summit and crossed by nu- 

 merous, closely spaced, almost threadlike, retractively curved, lines 

 of growth, which extend over both spire and base. In addition the 

 entire shell is marked with numerous microscopic, closely spaced, 

 incised spiral lines and the usual fine crisscross sculpture. The aper- 

 ture is broadly oval; the outer lip is decidedly expanded and re- 

 flected ; the columella is also expanded and reflected to form a moder- 

 ately large umbilcus. The parietal wall is covered by a thick callus. 



The type (U.S.N.M. no. 313720), collected by Pedro de Mesa at 

 Tara, Abra de Hog, Mindoro, has 6.5 whorls and measures: Length, 

 55.2 mm; greater diameter, 31.6 mm; lesser diameter, 26.3 mm. 



U.S.N.M. no. 313663 contains 23 topotypes, which yield the fol- 

 lowing data: 



1 Average. 



• Greatest. 



• Least. 



