FREE INSTITUTE OF SCIENCE 



619 

 TERTIARY FAUNA OF FLORIDA 



Group of A. antiqjiata L. {Anadara (Gray, 1847) Adams, 1858, in synonymy, 

 + Anomalocardia Adams, 1858, not of Schumacher, 18 17.) 

 Shell heavy, trigonal or oblong, inflated, with prosocoelous beaks, with 

 a wide area wholly covered by the ligament and usually with numerous 

 furrows for the resilium forming concentric lozenges ; teeth similar, in a long, 

 uninterrupted series, slightly larger and more oblique distally ; valves equal 

 and similarly sculptured; epidermis usually pilose and profuse. 



The young shell is often and the adult sometimes auriculate behind. 

 The transition to Scapharca s. s. is very gradual and complete. 



Group of A. pectuncidoides Scacchi. (liathyarca Kobelt, 1891.) 



Shell small, usually abyssal, inflated, with prosogyrate beaks and a rather 

 narrow but long furrowed area, the hinge- margin nearly or quite as long as 

 the shell ; teeth few, oblique, in two series, often separated by a wide gap in 

 the centre; the right valve smaller, the sculpture of the two valves often very 

 discrepant ; epidermis usually imbricated. 



These small deep-water Arks go back to the Eocene in time and form 

 a very recognizable group, related to Scapharca as Lissarca is to Barbatia. 



Subgenus LUNARCA (Gray) Adams. 



Lunarca (Gray, 1S40) H. and A. Adams, Gen. Rec. Moll., ii., p. 541, 1858. 



The only species known, L. costata Gray, is not unlike Argina, but has 

 no anterior taxodont teeth. These are replaced by a single, large, horizontal 

 tooth in the right valve, fitting into a socket in the left valve, forming 

 a remarkable exception to the usual rule in this familj'. 



In a manuscript of Stimpson's in my custody he queries whether this 

 shell is not a monstrous malformation of a specimen of Argina. I have 

 never seen a specimen and have never been able to purchase one from any 

 dealer, so I am unable to express a valuable opinion on this point, but perhaps 

 the question is worth investigation. 



In the descriptions of the species which follow, for convenience of recog- 

 nition the subgeneric name followed by the sectional name in parentheses will 

 introduce the paragraphs relating to each form. 



Area "Wagneriana Dall. 

 Plate 39, Figures 6, 7. 

 Area (Arcoptera) aviculceformis Heilprin, Trans. Wagner Free Inst. Sci., i., p. 98, pi. 13, 

 figs. 32, yza, 1886. 



