494 PROCEEDINGS OF THE NATIONAL MUSEUM. 



Georgia, in ooralliferous chert; Vaughan, Cooke, and Mansfield, 

 1914; station 7078, on the east bank of Fhnt Kiver, below the mouth 

 of Blue Spring branch, at Mascot Point, in chert blocks, by the same 

 coUectors, in 1914. U. S. Nat. Mus. Cat. No. 166713. 



The chief pecuHarity of this species and one by which it is easily 

 distinguished is the presence of strong radial ribs with channeled 

 interspaces, but without the strong almost spinose imbrications with 

 which we are familiar m analogous recent species. 



MODIOLUS (BRACHYDONTES) GRAMMATUS Dall. 



Modiolus {Brachydontes) grammatus Dall, Trans. Wagner Inst. Sci. Phila., vol. 



3, 1898, pt. 4, p. 794, pi. 30, fig. 2; Bull. U. S. Nat. Mus. No. 90, 1915, p. 127, 



pi. 26, fig. 4. 



Locality.— Station 7096, at Red Bluff, on the west bank of Fhnt 



River, 7 miles above Bainbridge, Decatur County, Georgia; Vaughan. 



Cooke, and Mansfield, 1914. U. S. Nat. Mus. Cat. No. 166753, 



Also in the Orthaulax pugnax zone at Ballast Point, Tampa Bay, 



Florida. U. S. Nat. Mus." Cat. No. 165184. 



MODIOLARIA (GREGARIELLA), species indeterminate. 



Localities. —Station 7074, at Hale landing, on the west bank of 

 the Flint River, 7 miles southeast of Bainbridge, Decatur County, 

 Georgia, in coralliferous chert; and station 7079, at Mascot Point on 

 the east bank of Fhnt River below the mouth of Blue (or Russell) 

 Spring branch, in chert blocks; Vaughan, Cooke, and Mansfield, 

 1914. U. S. Nat. Mus. Cat. No. 166754. 



Casts of a species probably belonging to the section GregarieUa, 

 but too imperfect to be specifically determined, were obtained as 

 above mentioned. Two species of this general type have been ob- 

 tained from the Orthaulax pugnax zone at Ballast Point, Tampa Bay, 



Florida. 



Genus ARCOPERNA Conrad, 1865. 



ARCOPERNA INFLATA, new species. 



Plate 85, fig. 1. 



Shell small, thin, mequilateral, the umbones nearly termmal, pro- 

 soooelous, small; the anterior dorsal slope abruptly descending, the 

 posterior nearly at a right angle to it, shghtly convexly arcuate; both 

 ends blmitly rounded, base ahnost straight; hinge edentulous, much 

 as in Musculus; inner margins of the valve apparently smooth, 

 interior disk concealed by matrix; the external sculpture of almost 

 microscopic radial striae over the whole surface, and concentric 

 emphatic restmg stages, irregularly disposed on the lower part of the 

 disk, to the number of two or three. Height, 12; length, 18.5; 

 diameter (double), 9 mm. 



Locality.— Kt station 7096, at Red Bluff, Fhnt River, on the west 

 bank, 7 miles above Bainbridge, Decatur County, Georgia; Vaughan, 

 Cooke, and Mansfield, 1914. U. S. Nat. Mus. Cat. No. 166714. 



