38 NEW UNIONIDiE, MELANID^, ETC., 



Unio Thoentonii. pi. 14, fig. 36. 



Testa Isevi, subrotunda. tumida, ad latere aliquanto planulata, ad basim compressa, valde inasquilaterali, 

 antice et postice rotundata ; valvulis crassis ; natibus valde elevatis, tumidis ; epidermide rufo-f'usca, 

 maculata ; dentibus cardinalibus crassis crenulatisque ; lateralibus percrassis subcurvisque ; mar- 

 garita alba et iridescente. 



Shell smooth, subrotund, swollen, slightly flattened at the sides, compressed at the 

 base, very inequilateral, rounded before and behind; valves thick; beaks very much 

 rais t swollen ; epidermis reddish brown, spotted ; cardinal teeth thick, crenulate ; 

 lateral teeth very thick and somewhat curved ; nacre white and iridescent. 

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

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

 My cabinet. 

 Diam. 1, Length 1-5, Breadth 1-4 inches. 



Shell smooth, subrotund, swollen, slightly flattened at the sides, compressed at the 

 base, very inequilateral, rounded before and behind ; substance of the shell thick, 

 slightly thicker before ; beaks very much raised, swollen and incurved ; ligament 

 short, thick and brown; epidermis reddish brown, maculate, the rays being 

 interrupted at each mark of growth, these latter being numerous and approximate, 

 smooth and shining above and striate and dull below ; umbonial slope raised and 

 rounded; posterior slope very oblique, flattened, cordate, with two indistinct im- 

 pressed lines from the beaks to the margin on each valve, and with a few very 

 indistinct interrupted rays; cardinal teeth rather small, thick and crenulate; lateral 

 teeth very thick, very oblique, somewhat curved and disposed to be double in both 

 valves ; anterior cicatrices scarcely distinct, rather small, very deeply impressed ; 

 posterior cicatrices distinct, rather small and well impre.s.sed; dorsal cicatrices. placed 

 above the centre of the cavity of thl ishell and on the base of the cardinal tooth ; 

 cavity of the shell deep and rounded ; cavity of the beaks very deep and angular ; 

 nacre silvery white and iridescent. 



Remarks. — A very interesting species, belonging to the group of which dollahel- 

 loides, (nobis,) may be considered the type. It is between that and cor, Conrad. 

 The rays consist of oblong spots formed by the interruption of the frequent marks of 

 growth, the larger marks being immediately before the umbonial slope. These rays 

 rise at the point of the beaks and make gentle curves over the disk towards the 

 basal margin, but cease when they reach the striate portion. The plate above the 

 cardinal tooth is very large. No specimen before me has perfect beaks, and therefore 

 the undulation is not observed. Neither were any received with the soft parts. I 

 have great pleasure in naming this after L. B. Thornton, Esq., who most kindly sent 

 me many new species from this habitat. 



