468 PROCEEDINGS OF THE ACADEMY OF |July, 



Occurrence. — -Ripley Formation: Dave Weeks Place, on Coon 

 Creek, McNairy County, Tennessee. 



Family TURBINIDSE. 



Genus SCHIZOBASIS gen. nov. 



Etymology: *%%£&, to split; /?«<"?, base. 



Type: Schizobasis depressa sp. nov. 



Shell of medium size, thick, porcellaneous, depressed and globose, 

 very low and smoothly rounded; protoconch lost in type species; 

 conch paucispiral, the component whorls increasing regularly and 

 rapidly in diameter; sculpture coarse and dominantly spiral; sutures 

 obscure; aperture circular, interrupted posteriorly by a slight shallow 

 siphonal notch and anteriorly by a slit which marks the entrance of 

 the anterior canal; outer lip not thickened, simple within; inner lip 

 excavated, heavily reinforced; anterior canal rather short with the 

 parallel proximate margins distorted so that it appears as a narrow 

 slit cutting across the base of the shell directly at right angles with 

 the axis; callus almost filling the umbilicus; umbilicus imperforate, 

 the umbilical region spread out in a trigonal area and flattened against 

 base of the columella, from which it is separated by a profound sulcus; 

 depressed umbilical keel marked by growth stages or often poorly 

 defined varices. 



This genus is characterized by depressed spire and by a peculiar 

 anterior canal which is short and deep and at right angles to the axis 

 of the shell and resembling a slit in the anterior part of the aperture. 

 It does not seem to be near anything heretofore described, and it has 

 been assigned to the family Turbinidse only after some hesitation. 

 The Turbinidse have a much depressed shell and sculptural and 

 nuclear characters much like Schizobasis, but none of that family 

 possess the short, well-defined canal which characterized this new 

 genus. The recent Turbo comutus, which is common in the Indo- 

 Pacific, has a very shallow anterior canal. The genus Sargana of 

 the Thaisidse has a much depressed spire, a shallow, posterior notch 

 and a narrow anterior canal inclosed in an umbilical keel which is 

 varicose and altogether possesses points analogous to Schizobasis. 

 Sargana has an entirely different sculpture and a much produced 

 anterior canal which are family characters, probably great enough 

 to bar Schizobasis from the Thaisidse. Turbo differs from Schizobasis 

 in being nacreous and in having no well-defined canal. There 

 is an undescribed species of Schizobasis that occurs at Eufaula, 

 Alabama. 



