CONCHOLOGICAL WRITINGS. 15 



Q. Obliquaria. 



89 Sp. Uniocalendis,{Obliq.calendis.—-lS2l.) Shell thick and 

 swelled, rounded, subtruncate behind, surface with broad flat wrinkles. 

 Length T-8, diameter 1-2, axis 1-5 of the breadth : outside yellowish, 

 inside iridescent and uneven. 



In Dick river, &c. Fine sp. beautiful nacre, rare, 2 inches. Near 

 to U. cyclips, bat smaller, less round, lamellar tooth quite oblique, 

 slightly curved as in the Plagiola, cardinal tooth striated ; proba- 

 bly a Sintoxia. 



90 Sp. Unio Venus, {Obliquaria Venus — 1820.) Shell oval 

 elliptic, thick and swelled, truncate behind with transverse wrinkles, 

 outside nearly smooth, of a reddish chesnut colour, inside lilac irides- 

 cent. Length 3-4, diameter 1-2, axis 1-3 of the length. 



In the Kentucky and Cumberland, very rare, 3 inches wide ; the 

 prettiest of all the TJnios, resembling a Venus. Lamellar tooth thick 

 erose obliqual. My Unio Elliptica sp. 8, is very near to this : both 

 are of S. G. Aximedia. 



91 Sp. Unio ^WeoZws, (Obliq. ditto. 1823.) Shell rather thin, 

 broad, elliptic lanceolate, attenuate and subacute behind, very com- 

 pressed or nearly flat, outside brown nearly smooth, inside bluish. 

 Length one half, diameter and axis 1-5 of breadth. 



At the falls of the Cumberland. Small, 2 inches, rare. Akin to 

 U. cuprea. Cardinal tooth small, bilobe, lamellar obliqual short. 



92. Unio teneltus, (Obliq. ditto. 1822.) Shell elliptic thin, nearly 

 equilateral, quite flat, margin erose, outside minutely striated, oliva- 

 ceous with square green spots, inside bluish. Length 4-T, diameter 

 1-7, axis 3-1 of the breadth. 



Exceedingly rare, seen only once in a stream of the Knob-hills of 

 Kentucky. Size one inch. It is an Aximedia which is to be a S. 

 G. of Obliquaria. Lamellar tooth obliqual very short, cardinal 

 bilobe small as in Leptodea. 



93 Sp. Unio bicolor, (Obliq. ditto. 1821.) Shell thick elliptic, 

 lanceolate, attenuate and subtruncate behind, with an obliqual ridge, 

 outside brown nearly smooth, inside yellow above, white beneath. 

 Length 1-2, diameter 1-3, axis 1-5 of breadth. 



In Kentucky river, 3 or 4 inches, akin to U. di'Zotato, but smoother 

 inside, different nacre, axis more anterior : more rare and beautiful. 

 Lamellar tooth obliqual thick. — The U. dilatata is however also an 

 Obliquaria and may be called Obi. violacea. 



