FROM PLIOCENE CLAY BEDS IN COSTA RICA. 371 



C. DisPAEiLis, d'Orb., La Sagra, v. 2, p. 283, PI. 21, f. 1-4. 



C. vieta, Guppy, Quart. Journ. Geol. Soc, v. 22, p. 580, PI. 26, f. 8. 



Although Mr. Guppy is loth to yield his name as a synonym (see Quart. Journ. 

 Geol. Soc, 1876), still I did not make the determination without due considera- 

 tion, and a review of the question only confirms my opinion. As Mr. Guppy says, 

 his shell is found in the Eocene, Miocene, and Pliocene of the West Indies, and 

 we now have it on the main land. 



C. LAVALEANA, d'Orb., La Sagra, vol. 2, p. 284, PI. 27, f. 9-12. 



Not rare in Costa Eica. Abundant in Santo Domingo, and living on the 

 Cuban and doubtless also on the Dominican coast. 



TELLINA, Linn. 

 T. (peron^oderma) alternata, Say, Journ. Acad. Phil., v. 2, p. 2T5. 



Another species from the coast of the United States. 

 T. (angulus) polita, Say, loc. cit., p. 276. 



Also from the North American coast. 

 T. (peroNuIia) appressa, n. s. 



Shell flattened, elongate; beaks subcentral, very slightly in advance of the 

 middle; cardinal margin regularly but very slightly convex from the beaks and 

 sloping gently to the posterior end, excavated and sloping in advance; anterior 

 end produced and subtruncated, not angular; base broadly and regularly convex. 

 Surface marked only by lines of growth. 



Length from 1 inch to 1 J inch. 



Most closely related to T. rufescens, Chemn., but differs in the regular con- 

 vexity behind the beaks; the base is also regularly rounded instead of being 

 slightly sinuated in advance, and the anterior end is broader and more sq'^arely 

 truncated. 



DONAX, Linn. 



D. MoENENSis, Gabb, n. s., PI. 47, fig. 72. 



Shell small, inequilateral, rounded triangular, beaks about two-fifths of the 

 length of the shell from the anterior end, which is broadly rounded below, nearly 

 straight above. Posterior cardinal margin straight, and sloping gently to the nar- 

 rowly rounded posterior end; base broadly and regularly convex. Surface orna- 

 mented by radiating lines, more or less visible, in different individuals, to the 

 anterior margin, always obsolete on the posterior part of the shell, but well 

 developed on the angle running from the umbones to the anterior basal angle. 

 Internal margin crenulated. 



