TRANSACTIONS OF WAGNER 

 6i8 



TERTIARY FAUNA OF FLORIDA 



neither of which were defined. So far as I have been able to discover, the 

 proper definition of all these names was first made in Adams's Genera in 

 1858, so that as regards priority all stand on a practically equal footing. 

 Anadara was not adopted by the Adams brothers, who placed it in the 

 synonymy of an unacceptable polynomial of Klein, and of all the names 

 Scapharca, as used by Adams, comprises by far the larger number of species. 

 I have therefore decided to adopt it in a subgeneric sense, reducing the less 

 tenable names to sectional rank. As thus understood, Scapharca comprises 

 the following groups or sections : 



Group of A. senilis Lam. [Senilia (Gray, 1840) Adams, 1858.) 



Heavy, trigonal, equivalve, with a short furrowed area ; beaks proso- 

 gyrate ; with a smooth epidermis; with the hinge-teeth separated by a sinus 

 into two straight subequal short series; both valves similarly sculptured; 

 inhabiting brackish water. 



Group of A. pexata Say. {Argina (Gray, 1840) Adams, 1858.) 



Thin, ovate-oblong, rounded; beaks prosoccelous, with the right valve 

 smaller, the cardinal area opisthodetic, or nearly so, and very narrow, the 

 hinge-teeth in two series — the anterior shorter, usually irregular or broken 

 up, the posterior longer, normal ; the epidermis imbricated and profuse ; 

 inhabiting salt water. 



Group of A. i7iequivalvis Brug. {Scapharca (Gray, 1847) Adams, 1858.) 



Moderately thin, elongate-ovate, with prosoccelous beaks, rather narrow 

 cardinal area, not wholly covered by the ligament and usually with concentric 

 resiliary lozenge-like grooving; tooth series uninterrupted, the teeth small, 

 similar, somewhat larger and more oblique distally; the right valve smaller, 

 the sculpture on the two valves usually similar or not markedly discrepant; 

 the epidermis much as in Argina. 



Group of A. incongrua Say. {Qinearca Dall.) 



Thin, trigonal, inflated, with erect beaks ; the cardinal area short, amphi- 

 detic, equilateral, set off by deep grooves from the rest of the sculpture, 

 smooth or transversely striated, without furrows ; hinge-teeth divisible into 

 two series, smaller proximally, larger and more oblique distally, often more 

 or less A-shaped ; the right valve smaller ; sculpture of the two valves 

 obviously discrepant ; the epidermis smooth or not pilose. 



