194 Bulletin '31 194 



Corbula extenuata Dall, PI. 58, Figs. 21-27 



Corbula (fossata var, ?) extenuata Dall, Trans. Wag., Ill, p. 844. pi. 

 36, fig. 6. 



Dall defines this form in the following terms : "This differs 

 irony fossata by being less high and more elongated, with two 

 very strong keels on the rostrum, the end of which is emarginate 

 between them ; the anterior keel projects below the ventral mar- 

 gin of the rest of the valve, with an emargination in front of it ; 

 the rostrum is produced, recurved, and sculptured as \n fossata ; 

 the beaks are small, pointed and incurved; the left valve is smooth 

 and very turgid. Long. 8, alt. 6, diam. of right valve 3.3 mm." 



We are led to believe this is far enough hoxn.fossata to be 

 regarded as a distinct species, not only on account of the length 

 of the right valve, but especially the greater length of the left 

 valve (see figs. 25-27) though this seems not to be quite in har- 

 mony with Ball's diagnosis. The species differs from Vao: fossata 

 type very much as gibbosa differs from tnurchisoni. 



Type.—\5. S. Nat. Mus. 



Horizon. — St. Maurice Eocene. 



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



Locality. — Orangeburg, S. C. (3-6 miles W. N. W.). 



Panopea porrectoides Aldrich, Pi. 59, Fig, i 



P. porredoides AlAx., Geol. Surv. Ala., No. i, 1886, p. 37 pi. 4, fig.3. 



Aldrich' s original description. — Shell thin, oblong, ventricose ; sur- 

 face marked by lines of growth ; anterior side expanded, posterior pro- 

 duced. Ventral margin nearly straight. Beaks incurved, pointed, wrinkled 

 by lines of growth. The posterior end widely gaping, and has a wedge- 

 shaped appearance. Tooth strong, blunt below, sharp above ; hinge line 

 short. 



Zf^a/z/y.^Baker's Bluff, Ala. ; Ferr. sand bed. 



The differences between this form and the Miocene P. porrectoides 

 Con., are very slight. 



We have no specimens of this species from the Claibornian 

 stage ; but have fine casts of the interior of somewhat broad- 

 er, larger specimens from the silicious limestone rock above New- 



