TRANSACTIONS OF WAGNER 

 1398 



TERTIARY FAUNA OF FLORIDA 



gaiiiesensis, and this is the earliest of our known Tertiary species. It is 

 attached by the left valve, is small, and concentrically simply lamellose. 



Chama involuta Guppy. 

 Chama involuta Guppy, Geol. Mag., dec. ii., vol. i., p. 444, pi. xvii., 'figs. 5a-c, 1874. 



Oligocene marl of Bowden, Jamaica ; Guppy, Henderson, and others. 



This is a small species, attached by the left valve, with the sculpture of the 

 valves discrepant. The attached valve has a vermiculately verrucose surface 

 with a few distant rows of low radial spines, sometimes obsolete ; the free valve 

 has low, fluted, concentric lamellse. 



Chama chipolana n. sp. 



Plate 56, Figures 19, 20. 



Oligocene marls of the Chipola horizon on the Chipola River and at Alum 

 Bluff on the Chattahoochee River, Calhoun County, Florida, Burns and Dall ; 

 in the silex beds at Ballast Point, Tampa Bay, and in the Oligocene sands of 

 Oak Grove, Santa Rosa County, Florida, Burns and Aldrich. 



Shell irregular in shape, but usually rounded, with the lower valve deep and 

 the upper one nearl}' flat, with a rotation of nearly two whorls in old speci- 

 mens; sculpture of the attached valve (usually the left but sometimes the 

 right) low, irregular, concentric lamellae and rounded radial ridges, which be- 

 come on the lamellae short channelled spines ; the radials vary in size but are 

 usually close-set ; the free valve has the concentric sculpture more or less sup- 

 pressed, the radials finer and more regular, hardly spinose ; there are frequently 

 radials on which the spines are better developed set at regular intervals, the 

 intervening radials without spines ; the adductor scars are rather short and 

 rounded ; there is a polished, smooth border between the pallial line and the 

 margin, the latter being finely radiall)' grooved or striate. The shell is com- 

 monly an inch in diameter but reaches twice or thrice that size in senile indi- 

 viduals, judging from fragments obtained. 



Two small valves are figured, since the older valves are invariably worn and 

 do not show the sculpture well. 



Chama tampaensis n. sp. 



Plate 54, Figure 6. 



Oligocene silex beds at Ballast Point, Tampa Bay, Florida ; Dall and Burns. 



Shell rather small, irregular, attached by the left valve; sculpture of con- 

 centric lamellae, on the attached valve sparse and irregular, not fluted or crenu- 

 lated, on the right valve rather more evenly spaced, though sometimes crowded. 



