GEOLOGY OF IvA COUNTY. 



119 



and a half to two W., ornamented with green 

 lines and bands radiatino- obliquely from um- 

 bones, pearly, bluish white within. Abundant. 



U. retusus. Oval, beaks curved, strongly retuse, 

 brownish. 



U. ebeneus. Oval, thick, black. 



U. coccineus. Oval, small. 



U. rectus. Long, straight, heavy, six to seven 

 L., polished, black, pink inside. 



U. anadontoides. Long, six to eight L., two 

 and a half to three W., milky to creamy white. 



U. metanerva. Three L., three W., triangular, 

 greenish yellow, very thick, beak promi- 

 nent. A sinus or hollow extends from beaks 

 across centre of each valve, surface marked 

 by strong concentric ridges and large, flat 

 topped tubercles, teeth strong, white within. 



U. cornutus. Triangular, two L., one and three- 

 fourths W., yellowish green, thick, with 

 about three large tubercules on each valve, 

 white within, surface often striped and dotted 

 with darker green. 



U. pustulatus. Oval, three L., two and a half 

 W., reddish brown, covered with small pus- 

 tules. 



U. verrucasus. Quadrate (squarish), three L., 

 three W., thick, flatfish, tuberculate, bluish 

 purple within. 



U. alsapus. Oblique, three and a half L., three 

 W., thick, heavy, dark brown, with a few 

 small projections or tubercules, white wHthin. 



U. tuberculatus. Oblique, five to eight L., three 

 to five W., dark brown, covered with small 

 tubercules, posterior margin notched. 



U. triangularis. Triangular, smooth, small, marked 



