31 



Unio perpasttjs. — Testa loevi, ellipticS., valde ventricosii, valde inaequilaterali, 

 postice obtuse biangulata, antice oblique rotundata ; valvulis crassiuseulis, 

 antice paulisper crassioribus ; natibus subprominentibus, inflatis; epidermide 

 luteo-fuscescente, superne micanti, inferne striata, eradiata ; dentibus cardi- 

 nalibus parviusculis, erectis, conicis corrugatisque ; lateralibus sublongis, la- 

 mellatis, corrugatis subcurvisque ; margarita alba et iridescente. 



Hab. — Coosa River, Alabama. E. R. Showalter, M. D. 



Unio gbanulatis. — Testa plicata, elliptica, subinflatd, valde inaequilaterali, 

 postice obtUBe angulata, antice rotunda; valvulis subtenuibus, antice paulisper 

 crassioribus, natibus prominulis, ad apices undato-granulatis ; epidermide tene. 

 broso-oliva, eradiata, transverse striata ; dentibus cardinalibus parvis, com- 

 pressis, obliquis, crenulatis, in utroque valvulo duplicibus ; lateralibus longis, 

 acicularis, tenuis subrectisque ; margarita purpurascente et valde iridescente. 



Hab. — Big Prairie Creek, Alabama. E. R. Showalter, M. D. 



Description of a new genus (STREPHOBASIS) of the family MELANID.E, and 

 three new species. 



BY ISAAC LEA. 



(Bead April 16th, 1861.) 



Family MELANIDiE. 



Genus Strephobasis. 



Testa cylindracea. Apertura subquadrata. Columella inferne incrassata 

 et retro-canaliculata. Operculum corneum, instar spirae. 



The mollusk for which I propose this genus, was sent to me by Wm. Spill- 

 man, M. D., of Columbus, Mississippi, and I have before me over a dozen 

 specimens from a third to nearly an inch in length. The very great number 

 of species of the genus Helania, makes it desirable to eliminate any group with 

 characters sufficiently distinct to permanently recognize it. The very remarka- 

 ble retrose callus at the base of the column, causing a lateral sinus, is charac- 

 teristic of this genus. 



Strephobasis Spillmanii. — Testa, laevi, cylindracea, crassiusculS, vel tene- 

 broso-fusca vel virente, valde vittata, nitidi ; spira obtusa, curta, ad apicem 

 carinata ; suturis irregulariter impressis ; anfractibus superne convexiusculis, 

 ultimo constricto ; apertura subgrandi, subquadrata, intus casrulescenti et 

 valde vittata; labro acuto, sinuoso ; columella sinuosa, ad basim incrassata 

 et retro canaliculate. 



ITnh. — Tennessee River. Wm. Spillman, M. D. 



