MIOCENE MOLLUSCA AND OKUSTACEA. 79 



Genus DONAX Linnaeus. 



DONAX VARIABILIS. 



Plate xiv ? figs. 19 and 20. 



Donax variabilis Say: Jour. Acad. Nat. Sci., 1st ser., vol. 2, p. 305; Tuom. and Holmes, 

 Plioc. Foss. S. Oar., p. 96, PI. xxiii, fig. G; ? Conrad, Proc. Acad. Nat. Sci. 

 Phil., 1862, p. 573; Heilprin, Proc. Acad. Nat. Sci. Phil., 1887, pp. 401 and 403. 



Say's description of this species is given as follows: " Shell triangular; 

 anterior margin obliquely truncate, cordate, suture a little convex; posterior 

 hinge margin nearly rectilinear, suture indented; base a little prominent, 

 beyond a regular curve near the middle; valves longitudinally striated with 

 numerous equal, parallel, regular, impressed lines, hardly visible to the 

 unassisted eye, and obsolete on the posterior margin; basal edge within 



crenate." 



The description given by Tuomey and Holmes is in nearly the same 

 language as the above and similarly expressed, and was evidently written 

 with Say's description before. them. The only specimen which I have seen 

 from the Miocene of New Jersey is an imperfect water-worn right valve, 

 but as far as the characters are preserved it accords perfectly well with the 

 recent shells found on our coast. 



Formation and locality : The specimen comes from the well-boring of 

 Mr. Woolmans, at Atlantic City, N. J., and is the property of the Academy 

 of Natural Sciences, Philadelphia. 



Family AMPHIDESMIID^l. 

 Genus AMPHIDESMA Lamarck. 



Amphidesma Burnsi, n. sp. 



Plate xiv, figs. 16-18. 



Shell small, compressed, and very thin in substance, transversely ellip- 

 tical in outline with nearly central beaks, which are small but somewhat 

 elevated or pointed; cardinal margins moderately sloping from the beaks 

 both anteriorly and posteriorly, the anterior side scarcely excavated in front 

 of the beaks; basal margin broadly curved and the extremities of the shell 

 nearly equally rounded, the posterior end being just perceptibly wider than 



