220 MYA. 



earinata, shell oblong-oval, two-angled before^ 

 rayed, hinge- margin strait, compressed, keel- 

 form ; teeth finely striate ; shell elongated trans- 

 versely ; epidermis greenish-yellow with broad 

 dark-green rays ; surface glabrous ; white, ira- 

 descent within. Dimensions about three inches 

 by two. 



prtflonga, shell much elongated transversely, nar* 

 row, thick, tumid, beaks flat ; lateral tooth 

 long, thin ; purple within ; epidermis blackish* 

 brown with fine interrupted wrinkles in longi- 

 tudinal rows. Dimensions about three inches 

 by one and a quarter. 



gibbosa, shell elongated transversely, thick gib- 

 bous ; lateral tooth very thick, incurved ; pur-* 

 pie within ; shell thick and heavy, suddenly 

 narrowed so as to appear beaked before, nar- 

 row and rounded behind, so as to appear sub- 

 cylindric ; epidermis blackish-brown finely stri- 

 ated and deeply wrinkled transversely ; purple 

 within ; lateral tooth very thick. Dimensions 

 about four inches by two. 



cuneata, shell ovate, wedgeform, thick, gibbous ; 

 disks tumid, anterior lunule furrowed ; lateral 

 tooth thin ; purple inside ; shell elongated, sub- 

 triangular, thick and heavy ; beaks low and 

 distant ; epidermis blackish-brown, subferru- 

 ginous, surface in fine wrinkles. Dimensions 

 three inches and three quarters by two and a 

 quarter. 



radiata, shell broad-ovate, thin, finely striated, 

 glossy rayed ; bluish-white within, or tinged 

 with red ; shell with the anterior side broad 

 thin ; fragile ; beaks slightly elevated and ap 



