370 PROCEEDINGS OF THE ACADEMY OF [April, 



in the very fine, markedly zigzag sculpture, there being three to four 

 lines to a millimeter. P. opisthogrammata, of the Floridian Pliocene, 

 is a "rounded-quadrate" shell with "the zigzag sculpture nearly 

 obsolete." 



Pitar cora n. sp. Pi. XXVIII, fig. 3. 



The shell is extremely thin, oval, with prosogyrate beaks at the 

 anterior fourth ; rather plump ; dorsal margin rather concave in front 

 of, and slightly convex behind, the beaks. Sculpture of fine, nearly 

 even concentric riblets, without radial striation. No denned lunule 

 or escutcheon. Interior unknown, but the valve-margins are smooth 

 inside. 



Length 35, alt. 26.5, diam. 18.5 mm. 



This species occurred as casts in a hard matrix retaining the shell 

 in places. P. hilli Dall is a longer, lower shell. 



*Macrocallista maculata (L.) (?). 



Cytherea (?) (Meretrix) dariena Conrad, Pacific R. R. Rep., VI, p. 72, PI. 5, 

 fig. 21. . 



"Isthmus of Darien." Identified by Gabb and Dall with the above 

 recent species, but the cast figured by Conrad seems to us uncharac- 

 teristic. 



*Pitar hillii Dall. 



Pitaria (Lamelliconcha) hillii Dall, Trans. Wagner Inst., Ill, p. 1,268, PI. 54, 

 fig. 7. 



Near Gatun. 



*Pitar circinata (Horn). 



Venus circinata Born, Mus. Test. Vindobon., p. 61. PI. 4, fig. 8. 



Pitaria (Lamelliconcha) circinata Born, Dall, Trans. Wagner Inst., Ill, 



p. 1269. 

 Cytherea funcea Guppy, Q. Journ. Geol. Soc. Lond., XXII, p. 582, PI. 22, 



fig. 13 (Oligocene of Cumana, Venezuela). 



Gatun (Dall). Also recent, on both coasts of Central America. 

 It is a more coarsely, sharply sculptured shell than P. cora. 



*Callocardia (Agriopoma) gatunensis Dall. 



C. (A.) gatunensis Dall, Trans. Wagner Inst., Ill, p. 1,260, PI. 54, fig. 1. 

 Toula, Jahrb., p. 723, PL 25, fig. 23. 



Gatun ; Monkey Hill. 



*Callocardia gatunensis multifilosa Dall. 

 Dall, /. c, p. 1,261, PI. 54, fig. 15. 

 Gatun, with the preceding. Also Ponton, Santo Domingo. We 

 have not seen this species, which should resemble Pilar cora rather 

 'closely, except as to the lunule. 



