56 STROBILOPS. 



lamellae there is a low whitish callus, irregularly trilobed in- 

 wardly, and on the apertural side having some tubercles along 

 V-shaped sinuses, or sometimes this pattern is not distinct. 

 The three thin, short and rather high basal folds, the middle 

 one largest, have their inner ends united by a low and nar- 

 row, irregularly-festooned radial callus. The size of the shell 

 is somewhat variable. 



Height 2.4, diam. 3.7 mm. ; 6 whorls ; umbilicus contained 

 314 to 314 times in diameter. 



Height 1.9, diam. 3.4 mm.; 5^ whorls; umbilicus contained 

 about 3^5 times in diameter. 



Wenz mentioned a var. hnmescens Mlldff., which, so far as 

 I know, has not been described. Specimens before me so 

 labelled do not appear distinguishable from those received as 

 typical quadrasi. 



APPENDIX TO STROBILOPSIDAE. 



Species discovered since the publication of the classification 

 of Strobilops necessitate an extension of the synopsis of sub- 

 genera and sections given on page 18 and of the key to Mexican 

 and Central American species on page 32. 



Key to Subdivisions of Strobilops. 



1. Parietal callus having a thickened, raised edge, prominent 



where the parietal lamella joins it ; parietal lamellae with 

 smooth or microscopically serrate edges, not nodiferous; 

 shell thin, carinate. Philippines. 



Subgenus Enteroplax, species Nos. 16-19. 

 Parietal callus not noticeably thickened or raised at the 

 edge. (2) 



2. Spire conoidal. (3) 



Subdiscoidal, the spire low, periphery rounded, umbilicus 

 wide; parietal lamellse with sparsely prickly or smooth- 

 ish edges, not nodiferous. 



Subgenus Discostrobilops, species 15. 



3. Umbilicus large, contained 3 or 4 times in the diameter (4) 

 Umbilicus decidedly smaller. (5) 



