238 NEW-YORK FAUNA — MOLLUSCA. 



the posterior placed near to the primary tooth, and shorter than the anterior one. Color, solid 

 white. Length, 1-1; breadth, l-l. Allied to the succeeding species. Georgia. 



A. radiata. (Say, lb. Vol. 5, p. 220.) Transversely oval-orbicular, a little compressed. Apex 

 nearly central, a little prominent ; posterior slope a little concave. Primary teeth two in each 

 valve; lateral teeth very distinct. Color, with rosaceous radii, sometimes obsolete ; within tinged 

 with yellow, and the rosaceous radii very distinct. Length, 0*9; breadth, l-l. East-Florida. 



A. lepida. (Id. lb. Vol.5, p. 221.) Shell very much compressed, subtriangular, very thin, pellucid, 

 equilateral, with concentric wrinkles and longitudinal striae, which curve on the anterior margin 

 towards the anterior edge, and behind towards the posterior slope. Cardinal teeth obsolete ; lateral 

 teeth prominent. Color, pellucid, Iridescent. Length, 0-2; width, 0.2. Soulh-Carolina. 



A. aqualis. (Id. lb. Vol.2, p. 307; Am. Conch, pi. 28.) Shell orbicular, slightly oblique, polished, 

 with numerous concentric wrinkles near the margin, obsclete on the disk and umbo. Primary 

 teeth two in the left valve and one in the other, which has no lateral tooth. Color, white. Length, 

 0*4. Not uncommon on the Southern Coast. 



FAMILY MYAD^. 



Shell often inequivalve, inequilateral, gaping at both extremities or at one only. Hinge 

 with an irregularly shaped tooth or teeth in one valve, received into an excavation in 

 the other, with an intermediate ligament. 



Obs. This group is [formed of part of the Family Pylorides of Blainville, and embraces 

 portions of the two families Myaires and Corbulees of Lamarck. It is represented on our 

 coast under three generic forms. 



GENUS PANDORA. Bruguieres. 



Animal with the mantle in the form of a sheath, and terminating behind in two tubes united 

 only at their bases, rather short, open in front for the passage of a large triangular foot, 

 which is thick and dilated at its end. Gills large, free behind ; or the two pair are united, 

 and terminate in a point in the tube. Labial appendices rather large, triangular, not 

 striated. Shell thin, pearly within, transversely oblong, inequivalve, inequilateral : right 

 valve flattened ; left valve more convex. Hinge with two diverging teeth in the flat valve,, 

 and corresponding grooves in the other. 



