48 Bulletin 4 16^ 



PEC TEN. 

 Peden alabainensis, PI. 2, fig. 3. 



Syn. P. (yPleicronedia) alabamensis Aid., Geol. Surv. Ala., 



Bull. No. I, p. 40, pi. 4, fig. 8. 

 P. (yAmussiuni) alabamejisis De Greg., Mon. Faun. Eoc. 



Ala., 1890, p. 183, pi. 21, fig. 26. 

 P. alabamensis Har., Geol. Surv. Ark., vol. ii of Rep't 



for 1892, p. 41. 



Aldricli' s original description. — "Shell small, suborbicular; up- 

 per valve covered with equidistant concentric lines which run 

 over upon the anterior ear; a few raised radial lines upon the 

 center and anterior side; ears small; right valve nearly smooth; 

 within both valves eight raised prominent rounded ribs, becom- 

 ing obsolete as they approach the beak. 



''Locality. — Matthews' lyanding, Ala. 



" Seems to unite Pleuronectia and Pecten. One specimen shows 

 concentric striae and ribs in the younger part of shell, these 

 becoming obsolete toward the ventral margin." 



Localities. — Arkansas: Marshall's well. Little Rock. Tubu- 

 lostium bed. 

 Alabama: Naheola; Matthews' Landing; Dale's 

 Branch. 



T)//^.— Collection of T. H. Aldrich. 



A VICULA. 



Avicula sp., PI. 2, figs. 4, a. 



We have obtained from the Midway stage but a few imperfect 

 casts of this genus, all from near the mouth of Sandy creek on 

 the Georgia side of the Chattahooche river. They represent but 

 one species, and are too imperfect to merit specific description. 



Specimens ^gured. — Paleontological Museum, Cornell Univ. 



PERN A. 



Perna cornelliana n. sp., PI. 3, figs. 2, 3. 



Specific characterization. — General form as indicated by fig. 2; 

 apical cartilage pits short and much wider than the interspaces, 

 the anterior two bounded below by an oblique tooth-like elevation; 

 posteriorly, pits and interspaces becoming of more nearly the same 

 width, while the pits are somewhat contracted above; muscular 



