282 DESCRIPTION OF NEW FRESH WATER AND LAND. SHELLS. 
Unio aratus, Pu. 42. Fig. 12. 
Testi, elliptica, crebre et transverse sulcatd, subcompressd, taequilaterali, posticé angulatd ; valvulis subcrassis ; 
natibus prominulis; epidermide pallido-luted; dentibus cardinalibus subgrandibus ; lateralibus longis curvisque ; 
margarita alba. 
Shell elliptical, closely and transversely furrowed, rather compressed, inequilateral, angular behind; valves rather 
thick; beaks somewhat prominent; epidermis’ pale-yellow; cardinal teeth rather large; lateral teeth long and 
curved ; nacre white. 
ae ee ee 
My cabinet. 
Diam. .3, Length .5, Breadth .7 of an inch, _ 
Shell elliptical, thickly, regularly, and transversely furrowed, rather compressed, ine- 
quilateral, angular behind; umbonial slope rounded; posterior slope with two raised 
curved lines extending from the beak to the posterior margin; substance of the shell rather 
thick; beaks somewhat prominent; ligament very short and very thin; epidermis pale- 
yellow over the whole disk, and without any appearance of rays; cardinal teeth rather 
large and disposed to be double in both valvés; lateral teeth long and curved; anterior 
cicatrices distinct; posterior cicatrices distinct; dorsal cicatrices placed across the centre 
of the cavity of the beaks; cavity of the shell rather shallow; cavity of the beaks rather 
shallow and angular; nacre white. 
Remarks.—A very remarkable little shell which may prove to be rather a young 
individual. The regular, transverse, closely-set furrows over the whole disk are very 
striking, it being the first species which I have seen with this perfect characteristic. 
The beaks are somewhat eroded, and I do not observe any undulations on them. Small 
ones may, perhaps, occur on perfect specimens. It seems to be somewhat allied to Unio 
stramineus, (Conrad,) but it differs somewhat in outline, and that species is not regu- 
larly furrowed, but rather transversely wrinkled, and is rather a large species, with 
beautiful undulations at the tip of the beaks. 
The habitat of this shell is not known. The person from whom I procured it could 
not even inform me whether it was exotic or not. 
