407 Costa Rica Miocene — Olsson 235 



Cal/istamaculataOsibh, iSSi, Journ. Acad. Nat. vSci. Phila. , 2nd series, 

 vol. 8, p. 372. 



Macrocallista {Chionella) maculata Dall, 1903, Trans. Wagner Free 

 Inst. Sci., vol. 3, pt. 6, p. 1256. 



Macrocallista maculata Brown and Pilsbry, 191 1, Proc. Acad. Nat. Sci. 

 Plila., vol. 63, p. 370. 



The Macrocallista ?nac2i.lata is a common and widely dis- 

 tributed fossil in the Costa Rican Miocene and is readily recog- 

 nized by its depressed, porcellaneous and highly polished shell. 

 In the usual sandy phases of the Gatun, the species is quite typi- 

 cal, but becomes high and broad in the coralline or transitional 

 phase. 



A variety cuneata has been proposed by Gabb to include 

 shells in which this posterior-dorsal slope is straight and not 

 humped as usual. We have seen no examples of this t5^pe. 



The Macrocallista maculata is a common recent species of 

 the West Indies, appearing for the first time, in the lower Mio- 

 cene beds of the Chipola River, Florida. 



Gatun Stage: Headwaters of Middle creek. 

 Rio Blanco. 



Genus CALLOCARDIA, A. Adams 



Subgenus AGRIOPOiVIA, Dall 

 CaMocardia gatunensis Dall Plate 32, figure i 



Callocardia {Agriopoma) gatunensis Dall, 1903, Trans. Wagner Free 



Inst. Sci., vol. 3, pt. 6, p. 1260, pi. 54, fig.i. 

 Callocardia {Agriopoma) gatunensis Brown and Pilsbry, 191 1, Proc. 



Acad. Nat. Sci. Phila., vol. 63, p. 370. 



A convex, cordate shell very abundant in the Gatun beds 

 of the Canal Zone, especially in the quarries at Mt. Hope. It 

 is a rare species in Costa Rica, but generally larger, more trian- 

 gular in outline and somewhat coarsely sculptured. These shells 

 are nearest to Ball's variety multijilosa. 



