150 GEOLOGY AND PALEONTOLOGY OF THE WEST INDIES. 



Antigona caesarina var. anguillana, new variety. 



(Plate 16, Figures 4 a, b.) 



Cytherea ccesarina Dall, Trans. Wagner Inst. Sci., vol. 3, pt. S, p. 1275, plate 53, fig. 5, 1903. 

 Antigona (aff.) caesarina Dall, Proc. U. S. Nat. Mus., vol. 51, No. 2162, p. 500, 1916. 



The following is a description of this variety. 



Shell orbicular, convex; sculpture of numerous low, flat, narrow, radial 

 riblets, separated by slightly wider interspaces, and of elevated, reflexed, 

 crenulated, concentric lamellae; lunule broad, cordate, extended anteriorly; 

 escutcheon long, wider in the right valve, defined on each valve by a deep sulcus. 



Length of the specimen figured (broken at the posterior end), 53 mm.; 

 height, 52 mm.; diameter of joined valves, 30.5 mm. 



The radial riblets are more prominent in the variety anguillana than 

 in the typical A. ccesarina and the lunule is more extended in front. 

 Perfect specimens might show other distinguishing characters. 



Antigona anguillana resembles A. tarquinia (Dall) from the Tampa 

 "silex" bed, from which it may readily be distinguished by its more 

 orbicular shape, greater inflation of the umbones, closer concentric 

 lamellae, and much broader, cordate lunule. Its sculpture, as well as 

 can be determined from the specimens at hand, is like that of the 

 Recent and Pleistocene A. listeri (Gray), from which it differs in the 

 greater inflation of the posterior dorsal slopes, which, in the latter 

 species, are flat or even slightly concave. A very closely related, 

 perhaps identical, form from the base of the Chattahoochee formation 

 near Bainbridge, Georgia, has been listed as A. (aff.) ccesarina by Dall. 



Localities. — Crocus Bay, Anguilla, station 6893; Blizzard Mill, 

 Antigua, station 6874; Vaughan. A fragment with similar sculpture 

 is from the chert interbedded with tuffs at St. Johns, Antigua, station 

 6855. The type of A. ccesarina is from the Chipola Miocene at station 

 2212, Ten Mile Creek, Calhoun County, Florida. 



Geologic horizon. — Oligocene. 



Type of A. ccesarina Dall. — U. S. Nat. Mus. No. 114754. 



Type of variety anguillana Cooke. — U. S. Nat. Mus. No. 167192. 



Chione spenceri, new species. 

 (Plate 15, Figures 1 a, b.) 

 The following is a description of this species: 



Shell ovate, moderately convex, with low, prosogyrate beaks and a sharply 

 defined, lozenge-shaped lunule with imbricating growth-lamellae; escutcheon 

 lanceolate, flat or slightly concave, and with fine growth-fines; radial sculpture 

 of minute, close, low, rounded ridges becoming obsolete at the anterior and 

 posterior ends; concentric sculpture of erect, evenly spaced lamellae, 24 on the 

 type specimen, smooth on the dorsal surface and on the upper part of the 

 ventral surface, but with a row of beads, contiguous to the radial ribbing, at 

 the base of the ventral surface. 



Length, 26 mm.; height, 23 mm.; diameter of joined valves, 15.5 mm. 



Localities. — Antigua, Spencer (type); Willoughby Bay, Antigua, 

 station 6881 ; Vaughan. 

 Geologic horizon. — Oligocene. 

 Type.—U. S. Nat. Mus. No. 163352. 



