Quarterly Journal of Conclwlogy. 391 



U. ANODONTOiDES, Lea. Common; Mississippi. Very smooth, 

 salmon color. 



U. ASPERRiMUS, Lea. Common; Mississippi. Variable in form, passing 

 one way \vA.opustulatus^ Lea, and the other into lachrymosus, 



U. CAPAX, Green. Very rare ; Mississippi. Drab color, very tumid, 

 high umbones; a fine shell. 



IT, coRNUTUS, Barnes. Abundant; Mississippi. Varies greatly in 

 color, some dark green and handsomely marked, others light 

 and not the slightest traces of green or epidermal markings. 



U. CRASSiDENS, Lamarck. Rare; Mississippi. Closely related to 

 ligamentinus, Lamarck on one side, and gibbosiis, Barnes, 

 on the other. Purple inside and dark epidermis, 12.7 cm. 

 long. 



U. EBENUS, Lea. Abundant; Mississippi. 



U. ELEGANS, Lea. Common; Mississippi and Cedar. Varies the 

 same as cornutus, also the interior white, rose, &c. Green 

 epidermis beautiful, seems to run into i?-igonus, Lea. 



U. ELLIPSIS, Barnes. Abundant; Mississippi. Closely like /«^^/«j-//, 

 Lea. 



U. GiBBosus, Barnes. Common; Mississippi. Almost always dark 

 purple inside but varies to white, commonly very convex 

 on dorsal edge and concave on ventral, but sometimes 

 straight and difficult to separate from rectus, Lam. 



v. GRACILIS, Barnes. Abundant; Mississippi and Cedar. Shell 

 generally very thin, epidermis from fine green rays to a 

 light color, interior white to purple, generally a dorsal wing, 

 teeth very light. 



U. GRANIFERUS, Lea. Common; Mississippi. Very thick, purple 

 inside. 



U. HiGGiNSii, Lea. Common; Mississippi. Silky epidermis, dark 

 rays from umbones, interior generally fine salmon color, 



