177 St. Maurice and Claibohne Pelecypoda 177 



shown by figs. 2 and 3, as well as similar forms from 5 miles N. 

 of Orangeburg, S. C. The angnlate and thinner shelled forms 

 from Keitt's Ravine (figs. 4-6) maj^ be placed here for the pres- 

 ent. 



Mactropsis sequorea Conrad, PI. 54, Figs- 7-9 



Erycina csquorea Con., Foss. Sh. Tert. Form., 1833, p. 42 ; pi. 19, fig. 



II of Harris' Reprint. 

 Madra grayi Lea, Cont. to Geol. , 1833, p. 42, pi. i, fig. 10. 

 Triquetra cequorea Con., Amer. Jr. Sci., vol, i, 1846, p. 218, pi. 2, 



fig. 5. 

 Mactropsis cequorea Con., Proc. Phila. Acad. Nat. Sci., 1854, p. 30. 

 Mactropsis csquorea Con., Amer. Jour. Conch., 1865, p. 5. 

 Mactropsis csquo7'ea Dall, Trans. Wag., Ill, 1895, p. 911. 



Conrad's best characterization (Amer. Jour. Sci. ). — Triangular, equi- 

 lateral, thick, plano-convex ; umbonial slope submarginal, angulated ; um- 

 bo flattened, apex acute ; anterior extremity acutely rounded ; posterior ex- 

 tremity obliquely truncated ; cardinal plate very thick ; fossett small, 

 ovate ; cardinal plate thickest under the anterior cardinal tooth. 



Claiborne, Alabama. 



A common species, the valves of which are always found separated. 

 The substance of the shell is remarkably thick. 



This is one of the very common lesser bivalves in the Clai- 

 borne "sand" at Claiborne. We have as 3^et found it from no 

 other horizon. 



7>/^.— Phila. Acad. Nat. Sci. 



Specimens figured. — Paleont. Mus., Cornell Univ. 



Mactropsis rectilinearis Conrad, PI. 54, Figs. 10-12 



Erycina rectilinearis Con., Foss. Sh. Tert. Form., 1833, p. 42 ; pi. 19, 



fig. 10 of Harris' Reprint. 

 Triquetra rectilinearis Con., Amer. Jr. Sci., vol. i, 1846, p. 218, pi. 2, 



fig. 8. 

 Mactropsis rectilinearis Con., Amer. Jour. Conch., 1865, p. 5. 

 Mactropsis rectilinearis Dall, Trans. Wag., Ill, 1895, p. 911. 



Conrad' s best characterication (Amer. Jour. Sci.). — Triangular, flat- 

 tened above, with coarse lines of growth ; posterior side subcuneiform, rather 

 longer than the anterior side, extremity subtruncated ; umbo much flat- 

 tened, apex acute ; posterior dorsal margin rectilinear ; basal margin a lit- 

 tle tumid near the middle. Claiborne, Ala. 



