118 



GEOLOGY OF LA SALLL COUNTY. 



3W., thicker than Capax, inflated, lines of 

 growth strong-ly marked, forming- concentric 

 ridg-es. 



U. ellipsis. Oblique, g-reenish, 2^2 in dia. , heavy. 

 MARGARITINA scarcely differing- from Unio, g-en- 



erally broad and flat, Marg-aritina complanata. 



Triang-ular, with folds, broad, flat. 

 M. corfrag-osa. — Squarish, undulations or folds 



broken, g-ivingr it a roug-h appearance. 

 M. marg-inata. — Ovate, thin, 3L., olive g^reen, mot- 

 tled with broken lines of a darker color, bluish 



within, becomes thicker with ag-e. 

 M. rug-osa. Oval, roug-hened by folds. 

 M. deltoidea. Triang-ular, smooth, anadenta, shells 



usually thin and smooth, hing-e without teeth. 



hence name A without and dens tooth. 

 A. edentula. Oval, smooth, 3L., black, polished 



within salmon, firm, with several undulations. 

 A. imbecillis. Oval, thin, brig-ht g*reen, frag-ile. 

 A. ovata. Oval, rather broad, flatfish. 

 A. corpulenta. Oval, larg-e, smooth. 

 U. occidens. Oval, yellowish, g-reen rayed vvith 



brig-hter g-reen, 4^L., 4W., larg-e ones thick. 

 U. nova eboraci. Oval, small, flat, yellowish, 



rayed with g-reen lines running- from beaks 



to marg-in, 2L., IW. 



U. spatulatus. Oval, g-reenish rayed with 



lines of darker g-reen. 

 U. lig-amentinus. Thick, heavy, 3 to 4L., 2 to 2^ W., 



brownish, rayed with g-reen, teeth prominent. 

 U. orbiculatus. Oval, squarish, solid, olive color, 



with narrow lines radiating- from beaks, umbo 



depressed, within white, ting-ed with salmon 



color. 



U. lutealus. Oval, flat to inflated, three L., one 



