MACTRID^. 43 



hinge slope with a rectilinear profile, and flattened oblong subcordate surface ; valves 

 •unequally wrinkled ; posterior margin rounded, shorter than the opposite margin, with a 

 reflected edge, and sub-marginal carinated line ; behind the middle of the disk, and some 

 distance before the elevated line, is a broad vitta of hardly perceptible longitudinal lines ; 

 within, a little undulated; posterior margin glabrous, with an obtusely indented, sub- 

 marginal line, corresponding with the exterior or carinated one." — Say. 



Raeta lineata, is not uncommon on the Southern coast, nor in the Post-Pleiocene as a 

 fossil. 



Plate VII. Fig. 12, Natural size. 



Locality. Simmons'. Museum, College of Charleston; Cabinet F. S. H. 



R A E T A C A N A L I C U L A T A . 

 Plate VII. Fig. 13. 



Lutraria canaliculata. Say, Jour. Acad. Nat. Sci., Vol. 2, p. 311. 



Lutraria canaliculata. Con., Am. Marine Conch., p. 46, pi. 10, fig. 1. 



Lutraria canaliculata, De Kay, Zool. New- York, Art. Mollusca, pi. 31, fig. 298. 



Lutraria canaliculata, Ravenel, Cat. Recent Shells, p. 2. 



Lutraria canaliculata, L. R. Gibhes, Tuomey's Geol. So. Ca., appendix, p. xxii. 



Raeta canaliculata, Con., M.S.S. 



Raeta canaliculata, Adams, Gen Moll., Vol. 2, p. 386, pi. 102, figs. 4, 4a. 



Lutraria canaliculata, Say's Conch. U. S., (Binney,) p. 102. 



Description. Shell transversely-oval, orbicular, very thin and fragile, white, inflated ; 

 valves equally, concentrically, and regularly grooved, with very faint parallel lines within 

 the grooves ; posterior margin short, sub-cuneiform, compressed ; a marginal, longitudinal, 

 irregular, sub-impressed line, between which and the edge, the grooves become mere 

 wrinkles ; posterior slope sub-rectilinear, hiatus considerable ; anterior margin regularly 

 curved, the slope convex ; within grooved as without ; anterior angle glabrous. — Say. 



This is a common shell of the Southern coast ; in the Post-Pleiocene beds of Simmons' 

 Bluff", we find numberless specimens in a perfect state, forming little groups of a dozen or 

 more individuals still in situ, occupying the vertical position in which they lived. 



Plate VII. Fig. 13. 



Locality. Simmons'. Museum, College of Charleston; Cabinet F. S. Jl. 



