FREE INSTITUTE OF SCIENCE 

 TERTIARY FAUNA OF FLORIDA 



This form is marked by a total disappearance of the radial stria; and the 

 development of fine, even, regularly spaced, concentric, elevated sculpture all 

 over the shell. I should have regarded it as a distinct species had it not been 

 for a few intcrgrading specimens. 



A fossil which may be a Plicatula, but of which the hinge is not accessi- 

 ble, is figured from the Midwayan Eocene by Harris, Bull. Pal. No. 4, p. 47, 

 pi. 2, figs. 2, 2 a, 1896. 



Plicatula densata Conrad. 

 riinitiiht ilcnsata Conrad, Proc. Acad. Nat. Sci. Phila., i., p. 311, 1843 ; Medial Tert., p. 



75, pi. 43, fig. 6, 1845; Proc. Acad. Nat. Sci. Phila., xiv., p. 582, 1863. 

 Spotnlylus inornatus Whitfield, Mioc. Pal. N. J., p. 34, pi. 5, figs. I, 2, 1895. 



In the Oligocene Vicksburg limestone at Archer, Florida, and the Num- 

 mulitic horizon at Ocala, Florida, Dall and Willcox; also in the Guallava 

 beds of Costa Rica, Hill ; in the Chipola beds on the Chipola River, and in the 

 lower bed at Alum Bluff; in the silex beds of Ballast Point, Tampa Bay, and 

 in the Alum Bluff sands at Oak Grove, Santa Rosa County, Florida, and the 

 Bowden marl, Bowden, Jamaica; in the Miocene marls of Cumberland County, 

 New Jersey, at Shiloh and Jericho. 



This species is distinguished from the later marginata of Say by its 

 usually rounder form and more numerous, less prominent plications. Occa- 

 sional specimens attached to a smooth surface by a considerable area do not 

 develop the plications, and one such has served as the type of Whitfield's 

 species. 



Plicatula gibbosa Lamarck. 



ifibhosa Lam., Syst. An. s. Vert., p. 132, 1801. 



ranwsa Lam., An. s. Vert., vi., p. 184, 1819; PHeilprin, Trans. Wagner Inst., 

 i., p. 102, 1887. 



t'lislatd (lal)]). C.eol. St. l)om., p. 257, 1873. 

 I'liiiiliila vcxillutii Ciiippy, (Icol. Mag., Dec. ii., vol. i., p. 444, pi. xvii., fig. 7, 1874. 



? Oligocene of Jamaica, Guppy ; recent in the Atlantic from Cape Hat- 

 teras, North Carolina, south to the West Indies and Rio de la Plata, Brazil. 



This species is contained in the Guppy collection from Jamaica, the 

 specimens showing the dark lines belonging to the species, but I suspect that 

 they were obtained from a later, perhaps a Pleistocene, deposit, as the explora- 

 tions of the Bowden marl by Messrs. Henderson and Simpson have produced 

 only .specimens of the P. densata from the Bowden horizon. 



