TRANSACTIONS OF WAGNER 



TERTIARY FAUNA OF FLORIDA 



near the base with rather sparse concentric imbrications ; ribs wider than the 

 interspaces, entire in the young; valves rounded; ears rather small with 

 concentric imbricated radii and rather deep byssal sulcus. 



Another form, which apparently has not yet taken on its adult character- 

 istics, has been described from the same beds by Whitfield under the name of 

 P. Rigbyi. It is said to have from twenty-two to twenty-six ribs with strong, 

 close concentric scales. It differs from Kneiskerni, according to Whitfield, 

 by its wider and stronger ribs with closer and more prominent imbrication. 

 (Whitfield, op. cit., p. 226, pi. 29, fig. 6, 1885.) 



Pecten (Chlamys) membranosus Morton. 

 Pectcn membranosus Morton, Org. Rem., p. 59, pi. 10, fig. 4, 1834. 



Pcctcii carolinensis Conr., Kerr, Rep. Gaol. N. Car., App., p. 18, pi. 3, fig. 2, 1875 ; not 

 Ly?-opecteii carolinensis Conr., 1875. 



Eocene of Jones County, Haldeman ; of Rocky Point and Wilmington, 

 North Carolina, Stanton ; Eutaw Springs, South Carolina, Conrad. 



This somewhat resembles the recent P. ornatis Lam., but is shorter and 

 more orbicular. There is no question of the identity of Mr. Conrad's P. 

 carolinensis with Morton's species ; I have compared the types. 



Pecten (Chlamys) 'wahtubbeanus n. s. 

 Plate 34, Figure 9. 



Claibornian and Jacksonian Eocene of Louisiana, Alabama, and Mis- 

 sissippi ; abundant at Wahtubbee ; Burns. 



Shell small, flattish, with small, unequal ears and rounded disk ; fourteen 

 or fifteen ribs carrying basally three densely finely imbricated, rounded threads, 

 the interspaces narrower with two crenulate threads; submargins with close, 

 fine, imbricate threads; ears prominent, with a deep, wide byssal notch, radi- 

 ately imbricate with coarse, elevated radial threads ; interior with shallow sulci, 

 the cardinal crura developed but no lirse on the disk. Alt. 22, lat. 22 mm. 



This species differs from the Claibornian P. Dcsliayesii Lea by its 

 threaded and less individualized ribs, its similarly sculptured valves, more 

 conspicuous notch, and concentric sculpture and smaller size when adult. P. 

 Jolmsoni Clark, from the Maryland Eocene, has more numerous ribs with 

 simpler sculpture, and which increase by intercalation instead of dichotomy. 

 A shell which I suppose to be the same as Clark's was obtained from the 

 Jacksonian of Clarke County, Mississippi, by Johnson. 



