﻿SVMT'HYNOTA 4^3 



Complanaria comprcssus Agassiz, Arch, fur Nat., I, 1852, p. 



Complanaria alasniodontina vStimpson, Shells of N. Eng., 1851, 



p. 14. 

 Unio alasvtodontiniis P.^-TEL. Conch. Sam.. Ill, 1890, p. 144- 

 Margaron (Unio) pressus Le-S Syn., 1852, p. 19; 1870, p. 29. 

 Unio prcssits H. and A. Adams, Gen. Rec. Moll., II, 1858, p. 



498. 

 Alasmodonta pressa P.aker. Tr. Ac. N. Sci. Si. L.. VIII, 1898, 



p. 76, fig.: Moll. Chicago, Pt. i, i8o8. p. 58, pi. vi. fig. 3; 



X. fig. 4. 

 Y-Av. plcbia (C. B. Adams). 



Shell very much smaller than the type ; base line straight or 

 a little incurved : posterior ridge rather high ; epidermis dull, 

 ashy, pale lurid or smoky-brown : hinge teeth imperfect. 



Length 48, height 24. diam. 13 mm. 



Vermont; Montreal River; Lal<e Superior. 



Type locality. Middlebury, Vt. 

 Unio cowpn-ssvs var. plebiiis C. B. Adams, F. W. and L. 



Shells of Vt., p. 16. 

 Symphynota coinprcssa var. plchius Simpson, Syn., 1900, p. 



"663." 



This is a very variable species in size, form, coloruig, and 

 the development of the teeth. Specimens before me have the 

 disk somewhat radially corrugated and this character is occa- 

 sionally seen on the posterior slope. In some cases, the beak 

 sculpture is strong, consisting of nearly straight bars like that 

 of .9. costata. The shell is usually less solid than that species, 

 but rather ponderous specimens occasionally occur. Ordmar- 

 ily the laterals are fairly well developed, but sometimes they 

 are nuich split up and blurred. I have seen specimens of what 

 I believe to be the variety plebia of C. R. Adams from the 

 northeast shore of Lake Superior, which were contributed by 

 Mr. las. H. Ferriss. They are very small, a little more inflated 

 than the type and dull smoky or ashy-green. 



