98 NEW UNIONlEvE OF THE UNITED STATES. 



oblique, although there is a tendency to that form. All the specimens being eroded 

 at the beaks, the character of the undulations cannot be ascertained. The most per- 

 fect specimen has a distinct double tooth in the right valve, but the others have only 

 rudiments of duplication, being affected by the erosion of the beaks. The specimens 

 have all been badly cleaned, being scraped to eject the deposit of oxide of iron, but it 

 is evident that there is a disposition on the whole side, anterior to the umbonial slope, 

 to be greenish in some specimens, and when perfect ones shall be found, I have no 

 doubt that this portion of the disks in some will be found to be of a fine green, con- 

 trasting with the yellow of the posterior slope. 



Unio Spillmanii. PI. 15, fig. 246. 



Testa ltevi elliptic;!, subinflata, inajquilaterali, postice obtuse angulata, antice rotundata; valvulis suberassis, 

 antice paulisper crassioribus ; natibus prouiinulis ; epidermide tenebroso-fusca vel luteo-fusca, ad um- 

 bones nitida radiata ; dentibus cardinalibus crassiuseulis, obtuse pyramidatis, eorrugatis ; lateralibus 

 lon»is crassis corrugatisque ; margarita vel alba vel salmonis colore tincta et valde iridescente. 



Shell smooth, elliptical, somewhat inflated, inequilateral, obtusely angular behind, 

 rounded before ; valves rather thick, a little thicker before ; beaks somewhat prom- 

 inent; epidermis brown or yellow brown, shining on the umbones, radiated; cardinal 

 teeth somewhat thick, obtusely pyramidal, corrugate ; lateral teeth long, thick and 

 rough ; nacre white or salmon color and very iridescent. 

 Proe. Aead. Nat. Sci. 1861, p. 39. 



ffab. — Luxpalila Creek, near Columbus, Mississippi. Win. Spillman, M. D. 



My cabinet and cabinet of Dr. Spillman. 

 Diam. IT, Length 1'8, . Breadth 29 inches. 



Shell smooth, elliptical, subinflated, inequilateral, obtusely angular behind, rounded 

 before ; substance of the shell rather thick, somewhat thicker before ; beaks somewhat 

 prominent ; ligament rather large and dark brown ; epidermis dark brown or yellowish 

 brown, shining'on the umbones, covered over the whole disk with nearly equidistant 

 rather dull rays, with two or three distant lines of growth ; umbonial slope slightly 

 raised and very obtusely angular; posterior slope rather narrow, elliptical, slightly 

 raised ; cardinal teeth rather thick, obtusely pyramidal, corrugate ; lateral teeth long, 

 thick and corrugate ; anterior cicatrices distinct, large and well impressed ; posterior 

 cicatrices confluent, large and moderately well impressed; dorsal cicatrices placed 

 immediately over the centre of the cavity of the beaks ; cavity of the shell rather 

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

 or salmon color and very iridescent. 



Remarks. — Some dozen specimens of this species have from time to time been sent 

 to me by Dr. Spillman. I have, until I got some better specimens recently from him, 

 feared it might be a mere variety of crocatus, (nobis), the females taking very much 



