Occasional Papers of the Museinn of Zoology 71 



DysHomia flexuosa (Raf.) = U. foUatus Hild., Agassiz, '52, p. 43. 



Truncilla {Dysnomia) foliata (Hild.), Simpson. '14, p. 18. 



Epiobhsma biloba Raf. = U. foliatus Hild., Frierson, '14", p. 7. 



Truii. flcxuosa (Raf.) = Tr. foliata (Hild.), Vanatta, '15, p. 557 

 ("type" examined). 



Tr. foliata (Hild.) =Obl. flcxuosa Raf. = £/>. biloba Raf., Walker, 

 '18'', p. 186 ("if identifiable"). 



Conrad and \'anatta have found that the so-called Rafin- 

 esqiie-Poulson "type"' of Hexuosa is the same as foliatus Hild. 

 The original description of Hexuosa mentions two gentle ele- 

 vations of the shell, and between them a i^'ide and Hat depres- 

 sion. This is a very prominent character of the species and 

 cannot be applied to any other shell. Also the description of 

 the margins of the shell as "flexuous" is significant. Thus the 

 specific name Hexuosa stands. 



As to biloba, its recognition is important with regard to the 

 validity of the subgenus Epioblasma (as against Dysnomia). 

 Ferussac is not sure about the identity of his authentic speci- 

 men of biloba. The phrase ''belly bilobed" has suggested the 

 idea that it is the female of Hexuosa, but this is not bilobed 

 below, but bisinuata, with only one large lobe. Also the 

 description of the shell as elliptical does not fit. for it is tri- 

 angular. Further, the beaks are not prominent, as described, 

 and nothing is said about the very striking feature, the two 

 ridges of the shell, and the deep and wide radial furrow. 



Thus the description of biloba is not recognizable, and with 

 this name also that of the subgenus, Epioblasma, goes into the 

 discard. 



