i83 Midway Stage 69 



Casts of this species are common in the limestone ledges of 

 the Midway on the Chattahoochee river above Sandy creek. 

 They are slightly longer than the types. Another specimen from 

 the basal layer is like the types. Higher in the Midway stage, 

 at Matthews' lyanding on the Alabama river, a thicker, higher 

 form occurs which is doubtless the descendant of the typical 

 form. Similarly higher forms occur in bed / at Hannah's, p. 18, 

 and a more nearly typical form was figured by the writer from 

 the Midway limestone of Arkansas; see Ann'l Rep't State 

 Geol. Surv. , 1892, vol. ii, pi. i, fig. 6. 



LUCINA. 

 Lucina claytonia n. sp., PI. 6, figs. 10, a. 



Specific characterization. — Size and general outline as indicated 

 by the figures (of different individuals); surface but slightly 

 striate near the umbones, but near the periphery showing several 

 (4 to 5) distinct halts in the growth of the shell, finely and 

 evenly striate between these growth lines; lunule small, im- 

 pressed, ligamental groove large and deep, bordered posteriorly 

 by a slightly elevated ridge in the right valve; cardinal teeth two 

 in each valve; anterior lateral faint in either valve; muscular 

 scars unequal as figured. 



The figures are from gutta-percha impressions. Imprints of 

 this species are very common in the limestone outcrop near 

 Clayton. 



This species varies somewhat in form but it generally has a 

 trace of a posterior truncation. The shell is rather thin. 



I know of no similar Eocene species with which this may be 

 compared. In general outline it resembles some of the very 

 large specimens of Mysia ungzdina from Claiborne but its muscu- 

 lar scars remove it far from that form. In some respects perhaps 

 this may be said to resemble L. symmetrica also from the Clai- 

 borne sands, but that is much larger, thicker, with differently 

 shaped teeth and ligamental pit and is more nearly circular in 

 outline; there are also several other points of difference. 



Locality. — Alabama: R. R. cut, lyi mi. N. B. of Clayton. 



Types. — Paleontological Museum, Cornell Univ. 



Lticina fortidentalis n. sp., PI. 6, figs. 11, a. 



Specific characterization. — Size and general form as indicated 

 by the figures; surface marked by ( 10 to 12) sharp, raised, con- 

 centric, lamellar rugae, between which are faint concentric lines; 



