248 Bulletin 39 420 



Uscari Stage: Hotel creek, C. R. 



Chione chiriquiensis. n. sp. Plate 32, figure 9, 10 



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

 smooth: escutcheon large, smooth and defined b)' an angled 

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

 lar ribs, like those of Chione 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 recur\^ed 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 the}- 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 abruptly cut 

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

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

 tureless. The interspaces are smooth, 



Gatun Stage: Water Cay. 



Section TIMOCLEA. Brown 



Chione grus Holmes, var. Plate 26, figure 21 



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



fig. 5- 

 Chione ( Tinioclea.) grus Dali, 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 closel}" related to C. grus Holmes. It is somewhat 



