110 INVERTEBRATA OF MASSACHUSETTS. 



Mr. T. J. Whittemore found several good specimens in the Mid- 

 dlesex Canal, not far from Charlestown. It is more common 

 in the Middle States. 



It is not difficult to distinguish this from any of the species found in 

 Massachusetts. The prolongation of the posterior extremity, which is 

 made more conspicuous by a contraction of the basal margin just be- 

 fore the tip, and its compressed and oblique teeth, are well marked 

 characteristics. But it is not so easy to distinguish smaller specimens of 

 this, from those of U. recttis and U. gibbosus, as the general form is the 

 same, and the prolongation of the tip in them is not very remarkable. 



UNIO RADIATUS. 



, Shell transversely oblong-ovate, broadest and angular behind, 

 inequilateral; epidermis ivrinkled^ brownish-olive, zoned and 

 rayed with dusJcy-green ; within bluish- white ; cardinal teeth 

 strong, erect, pyramidal. 



FIGURE 73. 



State Coll., No. 175. Soc. Cab., No. 2145. 



Mya radikta, GMELIN ; Syst., 3220. DJLLWYN; CataL, i. 51. WOOD; Gen. 



Conch., 109. 



IPnio radiata, LAM. ; An. sans Vert., vi. 535. DESK. ; Encyc. M6th. ; Fers, ii. 581. 

 ITnio radiatus, BARNES; Silliman's Journ., vi. 265, (young cariosus.) HIL- 



DRETH ; Silliman's Journ., xiv. LEA; Trans, timer. Phil. Soc., iii. 415, vi. 



127, pi. 15, f. 48, 49. (animal.) Synops. Naiad., 25. CONRAD; Unionida-^, 



pi. 10, f. 2. 



UJnio Virginiiina, LAM.; J3n. sans Vert., vi. 544. 

 My a oblongata, WOOD ; SuppL, pi. v, f. 2. 



Shell oblong ovate, broadest and angular behind, beaks near 

 the front, little elevated ; epidermis loosely and delicately wrin- 

 kled concentrically, olivaceous, with numerous rays of dusky- 

 green ; sometimes the wrinkles are also disposed in a radiated 

 manner. Hinge margin a little angular at the beaks ; anterior 

 extremity narrow, about one fourth the length of the shell, regu- 

 larly rounded, but the hinge margin turns downwards with a very 

 abrupt curve ; posterior side angular above, rounded at tip ; hinge 

 margin very little compressed ; basal margin regularly curved. 

 Interior white, iridescent posteriorly, with sometimes bluish or 



