40 NEW UNIONID.E, MELANID.E, ETC., 



Unio mundus. PL 14, fig. 38. 



Testa Isevi, obliqua, tumida, postice subangulata, valde insequilaterali ; valvulis crassis, antice crassioribus ; 

 natibus valde elevatis tumidis ; epidermide vel lutea vel luteo-fusca, maculata ; dentibus cardinalibus 

 parvis, crenulatis, compvesso-conicis; lateralibus sublongis obliquis, crassis subcurvisque ; margarita 

 alba et iridescente. 



Shell smooth, oblique, swollen, subangular behind, very inequilateral; valves 

 thick, thicker before ; beaks very much raised ; epidermis yellow or yellowish 

 brown and spotted; cardinal teeth small, crenulate, compressed, conical; lateral 

 teeth rather long, oblique, thick and somewhat curved ; nacre white and iridescent. 



Proc. Acad. Nat. Sci., 1857, p. 83. 



Eah. — Tuscumbia, Alabama, L. B. Thornton, Esq. 



My cabinet and cabinet of Mr. Thornton. 

 Diam. -9, Length I'l, Breadth 1-4 inches. 



Shell smooth, oblique, swollen, subangular behind, slightly flattened on the .sides, 

 very inequilateral; substance of the shell very thick, thicker before; beaks very 

 much raised and incurved ; ligament rather small and light brown ; epidermis 

 yellow or yellowish brown, with green spots on the sides formed of interrupted rays, 

 with numerous rather close lines of growth ; umbonial slope raised and rounded ; 

 posterior slope rather broad, fiattish, cordate, without rays, but with two indistinct 

 impressed lines, from the beaks to the margin, on each valve ; cardinal teeth small, 

 crenulate, compressed-conical ; lateral teeth rather long, very stout, oblique, some- 

 what curved and very thick on the plate ; anterior cicatrices confluent, small and 

 very deeply impressed : posterior cicatrices distinct, rather small and well impressed ; 

 dorsal cicatrices placed over the centre of the cavity of the beaks ; cavity of the shell 

 shallow and wide; cavity of the beaks rather deep and obtusely angular; nacre 

 pearly white and iridescent. 



Remarks. — This belongs to a very interesting group, of which davits, Lam. may 

 be considered the type. The beaks are not, however, so elevated, nor is it so wide. 

 It is allied to Tho7-ntonu, herein described, but is a smaller and more oblique species. 

 The rays are interrupted at each stage of growth, and thus become maculate. 



Unio tesserul^. pi. 15, fig. 39. 



Testa lasvi, quadrata, cuboides, valde tumida, valde ineequilaterali, postice obtuse angulata, antice truucata ; 

 valvulis crassis, antice crasgioribus ; natibus prominentibus, tumidis, incurvatis, ad apices rugoso- 

 undulatis ; epidermide mellea, micanti, radiis interruptis indutis ; dentibus cardinalibus parviusculis, 

 subconicis corrugatisque ; lateralibus curtis, nbliquis rectisque ; margarita argentea et valde iridescente. 



Shell smooth, quadrate, cubical, very much swollen, very inequilateral, obtusely 



