148 



ARCAD.E. 



A. pexata. 



anterior tcriniiiation of the scries of cardinal teeth ; at the other 

 extremity of the series, the outline of the shell, which is else- 

 where regularly rounded, has an obtuse angle ; the ligamentary 



area, or space Ijetwecn the beaks, 

 is very narrow, scarcely sepai'at- 

 ing them. Surface with thirty- 

 two to thirty-six radiating ribs, 

 rather Ijroader than the channels 

 between them ; these are trav- 

 ersed by minute lines of growth, 

 and interrupted by the more dis- 

 tinct overlapping zones of in- 

 crease. The whole is covered 

 by a thick, shaggy, fibrous epi- 

 dermis of a dark-brown color, 

 sometimes protruding from the interstices of the ribs in a fringe- 

 like manner. Interior white, the margin polished, and profoundly 

 scalloped l)y the alternate terminations of the rilts and grooves. In 

 continuation of the regular series of teeth are a few irregular pits 

 and prominences which fit into each other. Length, two and one 

 fourth inches ; height, two and one tenth inches ; breadth, one and 

 one half inches. 



The Area pr.rata has never been found to the north of Cape Cod. 

 I liave it from Martha's Vineyard ; it is not rare in Buzzard's Bay, 

 and is conunon al)Out Rhode Island. Osterville (^Haskell). 



It is distinguished from otlier North American species by the po- 

 sition of its beaks, its epidermis, its narrow area between the beaks, 

 and by its lieing equi valve. Its height increases posteriorly, so tliat 

 the interior of a valve has an ovate shape. 



Mr. Say remarks, that, wlien violently opened, an effusion of red 

 sanies issues ; and hence it has acquired the name of bloody clam. 



Area transversa. 



Shell rhomboidal, with from thirty-two to tliirty-five ribs ; beaks at the ante- 

 rior third of the series of teeth. 



Arm iramivfrsn, Say, Journ. Acad. Nat. Sc. ii. 269 (1822). — Stimpson, Shells of New 

 Eny-land, 8. — S. Smith, Shells of Long Island, 15, and Ann. N. Y. Lye. vii. — I)e 

 Kay, Nat. Hist. New York, 177, pi. 12, fig. 212. 



" Shell transversely oblong, rhomboidal, with from thirty-two to 

 thirty-five ribs placed at nearly the length of their own diameters 



