I202 TlvTRATLODON 



Tktraplodon scHOMBKRGiANrs (Sowerby). 



Shell biangular siibqnadrate. thin, concentrically wrinkled, 

 somewhat inequilateral; beaks moderately high and rounded; 

 posterior ridge elevated and rounded, ending in a blunt point 

 a little above the base of the shell ; post-dorsal slope elevated 

 into a low wing, which is rounded behind the ligament and 

 obliquely truncate behind ; umbonal region having rather feeble, 

 wavy, radial sculpture, which does not extend far over the 

 disk ; epidermis copper-colored ; teeth thin, lamellar. 



Length 50. height 40 mm. 



Guiana. 

 Castalia sclwinbcrgiana SowRrby, Conch. Icon., xvii, 1869, 



pi. I, fig. 3. 

 Tctraplodon scJionihcrgiauus Simpson, Syn., 1900, p. 864. 



A thin species with lamellar teeth, feeble umbonal sculpture 

 and coppery epidermis. 



Group of Tctraplodon multisulcatits. 



Shell small, somewhat compressed, with a moderate posterior 

 ridge, and covered throughout with delicate ridges ; teeth more 

 unionoid than in the typical Tetraplodons. 



Animal unknown. 



TF.TkAPr.OlK )N JT LM.'I'ISIU.CATUS ( Hupc) . 



Shell suhtriangular, somewhat compressed, inequilateral ; 

 beaks only moderately full, sculptured with numerous delicate, 

 radiating, more or less zigzag ridges, which extend over the 

 whole shell ; posterior ridge not greatly elevated, subangular 

 above, ending in a blunt point near the base of the shell ; an- 

 terior end narrowed, cut away above and below, narrowly 

 rounded ; dorsal slope elevated into a low wing, which is 

 obliquely trunate behind the ligament ; epidermis fuscous, 

 greenish-tinted; teeth vertically striate; nacre whitish, pearly. 



Length 42. height 30. diam. 23 mm. 



Brazil. 



