DESCRIPTION OF FIFTY-TWO SPECIES OF UNIONID^. 15 



much like subrotundus (nobis), and altogether it is nearly allied to that species. 

 None of the specimens have beaks perfect enough to display undulations at the 

 tips. 



Unio circum actus, pi. 4, fig. 11. 



Testa Isevi, rotundata, ad apices inflata, ad basim compressa, inaequilaterali ; valvulis crassis, antice 

 crassioribns ; natibus elevatis recurvatisque ; epidermide vel rufo-fusca vel castanea, maculata et 

 radiata; dentibus cardinalibus crassis, subcompressis sulcatisque; lateralibus percrassis, sabcurvis 

 corrugatisque ; margarita argentea et valde iridescente. 



Shell smooth, rounded, inflated at the beaks, compressed at the base, inequi- 

 lateral; valves thick, thicker before; beaks raised and recurved; epidermis reddish- 

 brown or chestnut, maculate and rayed ; cardinal teeth thick, somewhat compressed 

 and sulcate; lateral teeth very thick, somewhat curved and corrugate; nacre silver 

 white and very iridescent. 



Proc. Acad. Nat. Sci., 1871, p. 192. 



jjab. — Florence, Ala., Eev. G. White ; Holston Eiver, Miss Law. 



My cabinet, and cabinets of Mr. Wheatley and Dr. Lewis. 

 Diam. 1-1, Length 1-8, Breadth 1-9 inch. 



Shell smooth, rounded, inflated towards the beaks and compressed at the base, 

 inequilateral ; substance of the shell thick, thicker before ; beaks much elevated 

 ■ and recurved ; ligament thick, short and dark brown ; epidermis dark brown or. 

 chestnut color, with rather close marks of growth ; umbonial slope rounded, not 

 raised ; posterior slope narrow, cordate, in some specimens slightly maculate ; car- 

 dinal teeth thick, somewhat compressed, and disposed to be treble in the right 

 valve, sulcate ; lateral teeth very thick, slightly curved and corrugate ; anterior 

 cicatrice distinct, rather small and deeply impressed ; posterior cicatrices distinct, 

 rather small and well impressed ; dorsal cicatrices placed under the cardinal teeth 

 within the cavity; cavity of the shell rather shallow and wide; cavity of the beaks 

 shallow and obtusely angular ; nacre silvery white and very iridescent. 



Remarks. — This species so closely resembles Thorntonii (nobis) that I was 

 induced to place the first I saw with that species as a variety. Having now seven 

 or eight specimens before me, I am satisfied as to the value of the specific differ- 

 ence. All these specimens have a row of maculations immediately before the 

 umbonial slope, extending nearly to the margin. On the anterior half there are 

 rays and on the superior half maculations. This species belongs to the same group 

 with dolaheUoides, but this species is more rounded on the margin. None of the 

 specimens before me are perfect enough at the tips to present undulations. 



