6o Palakontographica Amkkicana 6o 



better be kept apart, at least until more is known." 



Dimensions. — Lon. +24,-29; alt. +7,-37; diam. 40 mm. 



Ocmrrence. — Upper Miocene of the Galveston artesian well (?); Pliocene of Port 

 Limon, Costa Rica; typical specimens from Pleistocene of Wailes Bluff, Maryland, Sim- 

 mons Bluff, South Carolina, and Brunswick, Georgia; recent from North Carolina south 

 to Texas, and (var. ? braziliana) from Texas south and east to Cape Roque and south to 

 Rio, Rio Grande do Sul, San Paulo, and Santa Caterina, Brazil. — Dull. Pleistocene of 

 New Orleans and Grand Chenier, Louisiana, and of Simmons Bluff and Georgetown, 

 South Carolina; recent from Point-au-Fer and Cameron, Louisiana, Galveston, Texas, 

 and from Florida. — C. U. Museum. A. brasiliana recent from Aspinwall. — C. U. 

 Museum. 



Area alcinia Dall 

 Plate X\', Figures i, 2 



Scapharca yCtmcarca) alcima Dall, Wagner Free lust. Sci., Trans., vol. % pt. 4, p. 635, pi. 31. 

 figs. ,S. 7, 189S. 



"Shell of moderate size, short, high, inflated, with elevated prosogyrate beaks; left 

 valve with thirty strong, squarely nodulous, radial ribs somewhat narrower than the in- 

 terspaces, without obvious concentric sculpture, front edge rounded, posterior less rounded 

 and longer, meeting the base at a rather blunt angle, this part of the shell being some- 

 what produced; right valve with twenty-seven less prominent ribs, of which the poster- 

 ior dozen have the nodules obsolete or absent and those on the anterior ribs somewhat 

 less marked than on the other valve; cardinal area short, wide, with the beaks incurved 

 over it; inner margin of the valves sharply fluted; hinge-teeth slightly larger and more 

 oblique distally, in general nearly vertical, close set, and about thirtj^-two in number, not 

 obviously divided in the center. Lon. 27, alt. 27, diam. 22 mm.; lon. of hinge-line 

 15 mm. 



"This is one of those species on the border-line of groups which make it so difficult 

 to divide the Arks into clear-cut sections; it has the hinge, cardinal area, and discrepant 

 sculpture of Cunearca; the valves are slightly unequal, and it seems most properly as- 

 signed to a place in this section. It is obviously a form ancestral to such species as Area 

 Chemnitzi "PhW. {A. bicops Orb.-\-A. atitillarum T>nnker, yide ls.ohe\t,-\- A. Orbignyi K.o- 

 belt), which is referred to Anomalocardia {=Anadara) by Ihering, and is found recent in 

 the West Indies. This species, which has been distributed under the (MS.?) name of 

 A. rhombica Rawson, is also inequivalve, with discrepant sculpture, and probably should 

 be referred to this section. 



"From A. Chemnitzi the present species differs by its larger size, more oblique 

 shape, narrower and more numerous ribs * * *." — Dall, 1S98. 



.4. Chemnitzi \s figured on Plate XV, Figures 3, 4. 



Ocairrence. — Pliocene marls of the Caloosahatchie at Alligator Creek, Florida. — Dall. 



