248 



Bulletin 39 



420 



Uscari Stage: Hotel creek, C. R. 



Ciisone chiriquiensis, n. sp. 



Plate 32, figure 9, 10 



Shell small, solid, depressed; lunule rather large, cordate, 

 smooth; escutcheon large, smooth and defined by an angled 

 ridge; surface of the disk sculptured with about 8, large, irregu- 

 lar ribs, like those of Chio7ie latilirata\ these ribs do not extend 

 to the edge of the escutcheon, but commence a short distance in 

 front leaving a narrow band which is smooth and sculptureless; 

 the ribs are of variable size, flat-topped and smooth; they are 

 rounded on their ventral side, but shelving or recurved back- 

 wards on the dorsal face; interspaces smooth or only sculptured 

 with fine growth-lines; interior of shell of moderate depth, with 

 a small pallial sinus and with a slightly larger posterior adduct- 

 or scar; basal margin finely crenulated. 



Length 13.75, height 12.50, diameter 9.50 mm. 



The few specimens which we have from Water Cay, are 

 probably immature, but they possess such distinctive characters 

 that the species cannot be mistaken. 



The heavy, irregular concentric ribs recall certain varieties 

 of Chione latilirata Conrad. They* differ in being abruptl}^ cut 

 off or flattened a short distance behind the dorsal-posterior angle 

 leaving a band as in C. paphia Linnaeus, but smooth and sculp- 

 tureless. The interspaces are smooth, 



Gatun Stage: Water Cay. 



Tapes grus Holmes, 1858, Post-Pliocene Fossils of S. Car., p. 37, pi. 7 



Chione {Timoclea) grus Dall, 1903, Trans. Wagner Free Inst. Sci,, 

 vol. 3, pt. 6, p. 1299. 

 We have but a single and not entirely perfect specimen of a 

 Timoclea closely related to C. grus Holmes. It is somewhat 



Section iliVSOCLEA, Brown 



Chione grus Holmes, var. 



Plate 26, figure 2 



fig. 5. 



