FRESH WATER AND LAND SHELLS. 277 



which enlarges the posterior basal margin; cardinal teeth very large, thick, spread out, 

 and deeply striate; lateral teeth short, thick, straight, with a large, flat plate separating 

 them from the cardinal teeth; anterior cicatrices distinct and deeply impressed; posterior 

 cicatrices confluent; dorsal cicatrices placed on the inner side of the plate; palleal cicatrix 

 impressed; cavity of the shell rather deep and small; cavity of the beaks very deep and 

 angular; nacre silvery white and iridescent. 



Remarks. — A single valve only was in the collection of Dr. Budd, and he thinks it came 

 from the west of Georgia. I have had it in my possession for several years, and deferred 

 describing it in the hope of getting more specimens; but in comparing it with its allied 

 species, metanever, Raf., tubcrosus, (Nobis,) and sparsis, (Nobis,) I have found it too dif- 

 ferent in outline and some other characters to place it with either. It is much more 

 enlarged on the posterior slope, which is almost winged, and it is without a groove on 

 that part, which the other three have. In this specimen the groove over the middle of the 

 valve is deeper than in the other species. The anterior portion is more enlarged than in 

 the others, and it has many rather low tubercles, the general character of which, over the 

 whole disk, is rather depressed and smooth. In the tubcrosus and mclanevcr the tubercles 

 are generally more raised and roughened. The tubercles on the posterior slope in this 

 specimen arrange themselves in curved rows, which, running to the margin, make it 

 crenulate. 



The lateral teeth are remarkably short, straight, and very thick. The intervening 

 plate between the cardinal and lateral teeth is exceedingly large and very flat. 



I dedicate this species to the memory of Rumphius, the author of " D'Amboinsche 

 Raritcitkamer." 



UNIO SAGITTIKORMIS. PI. XXII. Tig. 35. 



Testa few, valde transversa, compressd, ad latere planulatd, vahh : insequilaterali, postice acute angulata : 

 rti/iulis tubti mribut ; natibus pan is, prominidis, ml apices undvdatu : epidt rmide virido-fuscd, radiata : den- 

 libus cardinalibus parvis, compressis, crenvlatis; lateralibus prtelongis subrcctisque; margaritu purpurea et 

 iridesccnte. 



Shell smooth, very wide, compressed, flattened at the side, very inequilateral, acutely angularjjchind J valves 

 rather thin; beaks small, slightly prominent, undulated at the tip; epidermis greenish-brown, rayed ; cardinal 

 teeth small, compressed, crenulate; lateral teeth very long and nearly straight; nacre purple and iridescent. 



Hab. Oconee river, near Athens, Georgia, Major Lc Contc. 

 My cabinet and cabinet of Major Lc Conte. 

 Warn. .6, Length 1.2, Breadth 2.7 inches. 



Shell smooth, very wide, compressed, flattened at the side, very inequilateral, acutelj 

 angular behind; substance of the shell thin; beaks small, slightly prominent, undulated at 

 the tip and placed towards the anterior margin: ligament loni* and thin; epidermis brown- 

 isn, with numerous broad, dark-green rays, covering the whole disk, with rather distant 

 lines of growth; posterior slope somewhat compressed, with a Bingle raised line passing 

 from the beak to the posterior margin ; umbonial Blope rather acutelj angular-; cardinal 

 teeth rather small, compressed, crenulate, double in both valves ; lateral teeth long, nearly 

 roL. n. — 52 



