194 BuivLETIN "31 194 



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



Corbida {fossata var. ?) extenuata Dall, Trans. Wag., Ill, p. 844. pi. 

 36, fig. 6. 



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

 ixova. fossata b)^ 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 infossata ; 

 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 irom/ossata 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 the /ossata 

 type very much 2iS gibbosa differs from mtirchisoni. 



Type.~\J. S. Nat. Mus. 



HoTizo7i. — 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. porrectoides Mdr., Geol. Surv. Ala., No. i, 1886, p. 37 pi. 4, fig. 3. 



Aldrich' s origitial 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 

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

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

 short. 



Zoca/zVjl'.— Baker's Bluflf, 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- 



