47 St. Maurice and Ci^aibornk Pelkcypoda 47 



As regards the ribbing of this species, it should be noted that 

 while the individual is less than one-half inch in diameter the 

 ribs seem narrow, raised, more or less unevenly spaced and of 

 less width than the interspaces. The crossing of the concentric 

 lines causes a slight beading effect on very well preserved, very 

 small specimens. Later on, the ribs appear to widen and often 

 bifurcate and occupy the greater part of the shell surface. By 

 holding the shell in a strong side light it appears that one margin 

 of each rib is slightly higher than the other, so that a horizontal 

 section through, for example, the center of the shell, would show 

 the ribs sHghtly saw-tooth shaped. For the greater part of the 

 shell, the gentler slope is on the anterior side of the rib, but anter- 

 ior to a line drawn from the beak to the anterior-basal margin 

 this condition of affairs is reversed, i. e. the gentler slope on such 

 anterior ribs is on the posterior side. 



This species, so far as our collections go, seems to be con- 

 fined to the Claiborne stage of the Eocene. 



Tj'pe.—Vhila. Acad. Coll. 



Specimens Jig-tired.— Deposited in Paleont. Mus. Cornell 

 Univ. 



Horizo7i. — Claiborne Eocene. 



Locality. — Claiborne Bluff, Ala. 



Glycymeris idonea Conrad, PI. 20. Figs. 9-1 1. 



For synonymy, and Conrad's original description, see Bull. Am. Pal., 



II. p. 241. Also note : 

 Axinea idonea Con., A. J. Conch, I, '65, p. 12. 

 Pedunculus Broderipii var. radiafus de Greg. , Mon. Faun. Eoc. de 



1' Ala., '90, p. 194, pl.^zf^figs. 15, 16, (not 7-12, &c.). 

 Glycymeris idoneusDall, Trans. Wag. &c, vol. Ill, '95, p. 607. 

 Pedunculus idorteus Har., Bull. Am. Pal., I, '95, p. 22. 



Conrad's original description already referred to is fair ; but 

 without a figure, or access to type specimens, one naturally feels 

 some uncertainty about this species as the writings of de Gregorio 

 and Cossmann attest. The species however, need never be con- 

 founded with stami7iea on account of its greater obliquity, thicker 

 shell and comparatively greater depth. Theimarkings on the young 



