66 Bulletin 4 180 



even more prominent than in nicolletti typical, are much smaller. 

 After having collected large numbers of this genus from dif- 

 ferent horizons it will be possible to speak more positively of 

 these allied forms. 



Localities of this variety. — 



Tennessee: Hannah's, i^ mi. N. K. of Craines- 

 ville, bed b; Huddleston's, 3 mi. W. of Craines- 

 ville. 



Mississippi: Blue Mt., S, W. of Ripley; Reeves, 

 2>^ mi. N. W. of Walnut. 



Alabama: Naheola, Tombigbee river, (Best speci- 

 mens found here); i mi. N. of Prairie Bluff; 

 Dale's Branch, near Oak Hill; i mi. S. W. of 

 Clayton. 



Specimen figured. — Paleontological Museum, Cornell Univ. 



CHAM A. 



Chama gainesensis n. sp. , PL 6, figs. 4, a. 



Specific characterization. — General form and size as indicated 

 by the figure of the internal cast; valves of nearly equal size 

 and very similar throughout; umbones sometimes much stronger 

 than represented by the figure, distant; umbonal ridge fairly well 

 marked, anterior to which, or nearly in the central portion of the 

 valve, a slightly impressed, broad sinus extends from beak to 

 base; exterior with strong, wide, rather thick and irregular 

 lamellae. 



Locality. — GEORGIA: Uppermost bed of the Midway limestone 

 as exposed on the Chattahoochee river at Ft. 

 Gaines. Common. 



Types. — Paleontological Museum, Cornell Univ. 

 ISOCARDIA. 

 Isocardia mediavia n. sp., PI. 6, fig. 5. 



Specific characterization. — Size and general form as indicated 

 by the figure; beaks strongly in-rolled; umbonal ridge rather 

 sharp above, but less so below; shell very ventricose, the depth 

 of the valve figured being 12 mm.; surface smooth about the 

 umbo, but marked with concentric lines towards the basal margin. 



Traces of this species have been seen from the Midway lime- 

 stone of Texas, and from the clays of Black Bluff, Tombigbee 

 river, several years ago, but this is the first large, well preserved 

 valve found. 



