238 THE DEVONIAN OF MISSOURI. 



1874. Eatonia pecularis Billings, Pal. Fossils, vol. 1, pt. 2, p. 40, pi. 3a, fig. 2, a-c. 

 1894. Eatonis pecularis Hall and Clarke, Nat. Hist. N. Y. Pal., vol. 8 . pt. 2, pi. 61, figs. 



17-26. 

 1908. Eatonia pecularis Clarke, Mem. N. Y. State Mus., vol. 9, pt. 1, p. 172, pi. 29, 



figs. 1-13. 

 1913. Eatonis pecularis Schuchert, Geol. Surv., Md. Low. Dev., p. 372, pi. 65, figs. 

 23-28. 



Description — Shell commonly small, and a little longer than wide, but in some speci- 

 mens the length and breadth are the same. An average individual measures 17 mm. 

 in length, and 15 mm in width. The dimensions of the largest specimen observed are: 

 Length 25 mm., width 22 mm. Shell distinctly ovate in outline, the cardinal margins 

 diverge from the beaks and form a flattened oval area on each side of the shell. 



Pedicle valve depressed convex posteriorly from the middle of the shell toward 

 the beak, but gently concave toward the margins of the cardinal slopes, where it be- 

 comes abruptly inflected. Anteriorly the valve is prolonged into a long linguiform 

 extension. 



Brachial valve convex, the surface sloping abruptly to the lateral margins. To- 

 ward the anterior margin the middle is elevated into a fold. Margins of both valves 

 serrated, the serrations on the brachial more prominent than those on the opposite 

 valve. 



Surface of entire shell covered with fine, bifurcating striae, 5 to 6 of which occupy 

 the space of 1 mm. 



Remarks — -This form, next to the Spirifers, is perhaps the most abundant fossil 

 in the Little Saline beds, and it is the only species which occurs commonly with the two 

 valves in articulation, complete specimens being found in a splendid state of preserva- 

 tion. Many of the shells are larger than those from the Oriskany beds of New York, 

 and resemble rather in size those from the Grand Greve limestone of Gaspe, Canada, 

 exhibiting a similar variation in shape and size. 



This species is characterized by the linguiform projection of the anterior margin, 

 the strong inflection of the pedicle valve along the cardinal slopes, and the serrated 

 margins of the valves. 



Horizon — Lower and upper beds. 



Figured specimens No. 27467 Walker Museum,. 



Eatonia plicata sp. nov. 

 Plate 63, figures 1-4. 



Description — Shell small, relative length and width variable, although the length 

 is commonly greater than the width. The holotype which is an average-sized individual 

 measures 13 mm. in length and 1 1 mm. across its greatest width which is slightly anterior 

 to the middle of the shell. The form is elongate oval in outline, with the cardinal 

 margins converging abruptly to the beak. Anterior margin serrated. 



Pedicle valve depressed convex in the umbonal region, and flattening out towards 

 the middle into a sinus which is prolonged into a long linguiform extension of the anterior 

 margin. Toward the lateral margin the shell becomes inflected somewhat abruptly. 

 Umbonal region scarcely differentiated; beak small, acute, incurved slightly, the apex 

 pierced by a round foramen. 



Brachial valve rather highly convex; near the anterior margin the middle becomes 

 elevated into a fold. Umbonal region arched; the beak larger than in the opposite valve 

 and more rounded. 



Surface of both valves marked by simple radiating, coarse, angular plications, from 

 16 to 18 present on each valve, which are separated by deep narrow interspaces. The 



