18 • NEW UNIONID.^ OF THE 



long, lamellar, rather thick and slightly curved; nacre either white, salmon or pur- 

 plish and very iridescent. 



Proc. Acad. Nat. Sci. 1859, p. 171. 



Hah. — Flat Rock Creek near Columbus, Georgia. G. Hallenbeck. 



My cabinet and cabinet of Mr. Hallenbeck- 

 Diam. 1, Length 1-7, Breadth 3-6 inches. 



Shell smooth, transverse, rather inflated, flattened at the side, obtusely angular 

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

 thick, sliglitly thicker before ; beaks a little prominent, at the tips furnished with 

 close, parallel undulations which are angular on the umbonial slope ; ligament rather 

 long, thick and light brown ; epidermis reddish brown, sometimes with numerous fine 

 green rays, sometimes without any ; umbonial slope somewhat raised and obtusely 

 angular ; posterior slope somewhat broad, with two obscure grooves from the beaks 

 to the posterior margin on each valve; cardinal teeth rather large, compressed some- 

 what raised, striate, crenulate and double in both valves ; lateral teeth very long, 

 lamellar, rather thick and slightly curved ; anterior cicatrices large, distinct and 

 deeply impressed ; posterior cicatrices large, confluent and slightly impressed ; dorsal 

 cicati'ices placed immediately over the cavity of the beaks; cavity of the shell rather 

 shallow and wide ; cavity of the beaks very shallow and rounded ; nacre either white, 

 salmon or purplish, sometimes consisting of either two of these colors; nacre very 

 iridescent. 



Remarlca. — I have about a dozen of this species of various ages from Mr. Hallen- 

 beck. It is nearly allied to Hallenbedcii on one side and salebrosus on the other. It 

 is transverse like the latter, but is not biangular behind as that species is. It is some- 

 what oblique and angular on the umbonial slope like the former, but it is much moi'e 

 transverse. Some of the specimens, particularly the middle aged and young, have 

 numerous green rays, while the older ones with decorticated beaks and worn nmbones 

 are quite destitute of them. The nacre is generally very beautiful. Each specimen 

 usually has two colors. The most common is light purple on the margin, and salmon 

 in the centre of the cavity, and in the beaks; sometimes white takes the place of the 

 salmon color. One of the specimens is all white and another is all purple. Two of 

 the younger specimens have the green rays so close that the disk presents a quite 

 green surface. 



UxiO VIRIDIHADIATUS. PI. 53, fig. IGl. 

 Testa ]-x\i, late elliptica, compressa, postice dilatata et obtuse angulatil, antice regularifer rotunda, valde 

 inEequilaterali ; valvulis subtenuibus ; natibus prominulis, ad apices minute et irregulariter undulatis ; 

 epidermide subnitida, radiis crebris capillaris; dentibus cardinalibus paryis, crenulatis, in utroque val- 

 vulo duplicibus ; lateralibus longis, lamellatis subrectisque ; margarita purpurea et valde iridescente. 



Sliell smooth, broadly elliptical, compressed, flattened behind and obtusely angular, 



