1353 



of the genus. These characters, which belong to the undifferentiated types of 

 the Eocene, gradually fade out until the recent species of Lucina have only 

 incremental concentric sculpture, and the radial striation is entirely, or almost 

 entirely, absent. 



The young specimens of this species are very delicate shells, on which the 

 concentric threads are more distant than in the portion of the shell subse- 

 quently formed, and the radial sculpture very marked, so that at first sight 

 they appear quite distinct from the adults, which are abundant but poorly 

 preserved in the lower bed at Claiborne Bluff. It is to this immature form 

 that the names given by Clark and Harris apply. 



Lucina sp. indet. 



Internal casts of a species of Lucina sixty-five millimetres long and more 

 inflated than L. subvexa were obtained by Burns on Stout's Creek, eight miles 

 below Fort Mott, Orangeburg County, South Carolina, in strata said to be 

 Eocene. They are too imperfect for description. What may be the same 

 species, also represented only by internal casts, has been received from lime- 

 stones of Claibornian age near the iron mines of Santiago de Cuba in the rail- 

 way cut two hundred and fifty feet above the sea, in beds of uncertain, possibly 

 Eocene, age on the islands of St. Kitts and Trinidad, West Indies, and from 

 the Oligocene horizon at Clairmont, St. Ann's, on the island of Jamaica. This 

 last specimen seems more profusely concentrically striated externally and some- 

 what less inflated than those previously mentioned and may belong to a distinct 

 species. It would probably belong to the same horizon as beds containing a 

 profusion of similar casts, badly preserved, at Chattahoochee Junction, where 

 the railway bridge crosses the Chattahoochee River near the Georgia-Florida 

 boundary line. 



Lucina janus n. sp. 

 PLATE 51, FIGURE 9. 



Oligocene of Chipolan age at Sopchoppy Creek, Wakulla County ; Preston 

 Sink ; the Chipola River ; the lower bed at Alum Bluff on the Chattahoochee 

 River, and in Walton County, Florida. 



Shell orbicular, plump, nearly equilateral ; beaks low, slightly prosogyrate 

 over a small, deeply impressed, narrowly lanceolate lunule ; anterior hinge-line 

 somewhat ascending, suddenly rounding into the curve of the anterior end, 

 forming an ill-defined wing, which has irregular marks of compression where 

 it joins the body of the shell ; the posterior dorsal descends slightly in a right 



