THE NAUTILUS. 115 



The shells of Anomia have one valve convex and the other flat or 

 a little concave ; the flat valve is perforated and the plug which tills 

 the hole and partly attached to the valve. The shells are seldom 

 found i'rt'( j hut generally attached to oysters or other shells or stones. 

 There are twenty species, two of which inhabit New England. 

 ( To be continued.) 



DESCRIPTION OF A NEW UNIO FROM TENNESSIE. 



BY WM. A. MARSH, ALEDO, ILLINOIS. 



Quadrula andrewsii, n. sj). Shell smooth, triangular, solid, 

 heaks swollen, incurved, shell very inequilateral, compressed and 

 striate at the base, obliquely rounded before, obtusely biangular be- 

 hind, ligament rather short, light brown, epidermis reddish brown, 

 maculate, growth lines numerous^ rather rough, umbonal slope 

 slightly rounded, posterior slope flat, cordate, with very indistinct 

 lines from beaks to basal margin, beak sculpture unknown, cardinal 

 teeth thick, very much sulcate, single in right, double in left valve, 

 lateral teeth thick, short, and slightly curved, anterior cicatrices 

 small and deep, posterior cicatrices distinct, small and deep, shell 

 cavity rather deep, cavity of the beaks deep and angular, nacre silver 

 white and iridescent. 



Diameter 1.1 ; length 1.6 ; breadth 2. 



Habitat : Holston river, Tenn., Mrs. Geo. Andrews. 



Remarks: Several years ago Mrs. Geo. Andrews, of Knoxville, 

 Tennessee, sent me a number of these shells. I never knew where 

 to place them, but recently, on sending some of them to Mr. Simp- 

 son for examination, I was satisfied they were distinct. They be- 

 long to the group of which trigonus, Lea, is the type, but in no 

 way do they resemble that species. There is no species which they 

 closely resemble, except globatus, Lea, but it is a very much less 

 inflated shell than that species, having a different colored epidermis, 

 rougher and coarser growth lines, at least one-half of the disk is 

 covered with wide, dark green spots ; between these rows of macula- 

 tions are very narrow, dark green interrupted rays. 



The outline of globatus is rounded, while my shell is triangular. 



