10 NEW UNIONID^ OF THE 



Remarlcs. — I have a number of specimens of this s^^ecies before me, many of which 

 differ in several phases. When I -first received part of them some two years since, I 

 considered them a variety of subellijysis (nobis), but there are several characters which 

 separate it from that species. It is smaller and is more disposed to being nearly straight 

 on the basal margin. It has also a peculiarity in nearly all the specimens of having 

 very faint rays on the sides and on the anterior portion, while the posterior portion 

 has larger, greener and more closely set rays. The rays are usually wavy, and some- 

 times consist of a bundle of capillary lines. Most of the specimens are more or less 

 sulcate on the anterior slope. The females are smaller than the males, and are en- 

 larged on the umbonial slope, somewhat like rutilans (nobis). Only one of the speci- 

 mens was perfect enough to observe the character of the undulations on the tips, and 

 these were small, numerous and very regular. 



In outline it is very near to interceJens (nobis), but not so regularly elliptical, and 

 that is a smaller species and usually purplish or salmon colored in the nacre, while 

 this is always white, at least I have never seen it of any other color. 



I have not had the opportunity of examining the soft parts of this species, but Mr. 

 Hallenbeck informs me that he examined a female in October. He says that " the 

 posterior half of the branchiae Avas well filled with young. It was white and exhibited 

 the ril)bed appearance of exiguus, but differed from exigutts, suhellipsis, rutilans, &c., 

 in the basal margin not being colored, that is, being all white and simple. The em- 

 bryonic form is near to rnt'dans, the dorsal line being a little shorter, side mar- 

 gin to the middle gently sloping, and then nearly straight to the rounded basal mar- 

 gin — no hooks." 



Unio Hallenbeckii. pi. 51, fig. 154. 



Testa laevi, suboblonga, compress:!, ad latere planulata, valde inaequilaterali, postico subbiangularl, antice ob- 

 lique rotundata ; valvulis subcrassis ; natibus prominulis, ad apices crebrc et concentrice undulatis ; cpi- 

 dermide rufo-fusca, micante, obsolete radiatii; dentibus cardinalibus subgrandibus, compressis, erectis, 

 crenulatis, in utroque valvulo duplicibus; lateralibus Itogis, crasisis rectisque ; margarita vel purpurea 

 vel salmonis colore tincta et valde iridescente. 

 Shell smooth, somewhat oblong, compressed, flattened at the sides, very inequilateral, 

 subbiangular behind, obliquely rounded before; valves rather thick; beaks slightly 

 prominent, closely and concentrically undulate at the tips ; epidermis reddish brown, 

 shining and obscurely radiate; cardinal teeth rather large, compressed, erect, crenu- 

 late and double in both valves ; lateral teeth long, thick and straight ; nacre purple 

 or salmon color and very iridescent. 



Proc. Acad. Nat Sci. 1859, p. 170. 

 Hah. — Flat Rock Creek and Four Mile Creek near Columbus, Georgia. G. Hallen- 

 beck and Bishop Elliott. 



My cabinet and cabinets of Mr. Hallenbeck and Bishop Elliott. 

 Diam. -9, Length 1-7, . Breadth o inches. 



