438 MISSISSIPPIAN BRACHIOPODA 



EUMETRIA ALTIROSTRIS (White) 



Plate LXXVI, Figs. 7-11 



1862. Retzia (Acambona?) altirostris White, Proc. Boston Soc. Nat. Hist., 



vol. 9, p. 28. 

 1897. Eumetria (?) altirostris Schuchert, Synop. Am. Foss. Brach.. p. 



222. 

 1900. Eumetria altirostris Weller, Trans. St. Louis Acad. Sci., vol. 10, 



p. 74, pi. 2, figs. 18-19. 



Description. Shell of medium size or smaller, subovate in outline, 

 longer than wide, the greatest width anterior to the middle, the lateral 

 margins diverging in nearly straight lines from the beak to nearly the 

 line of greatest width, the anterior and antero-lateral margins describing 

 a nearly semicircular curve, the hinge-line very short. The dimensions of 

 a nearly complete, large individual are : length of pedicle valve 23.5 mm., 

 length of brachial valve 20 mm., greatest width 20.5 mm., thickness 14 

 mm., length of hinge-line 5 mm. 



Pedicle valve most convex posterior to the middle, the umbonal region 

 prominent and projecting notably beyond the hinge-line, the median line 

 of the valve arcuate or curving with a gradually decreasing curvature 

 from the beak to the front, the surface curving rather abruptly from the 

 median portion of the valve to the lateral margins, and posteriorly 

 inflected towards the cardinal extremities; the beak prominent, pointed 

 and incurved, and pierced by a large, subcircular foramen which 

 encroaches upon the umbonal region of the valve; the cardinal area 

 small and arched, its lateral margins sharply defined, sloping regularly 

 from the sides of the beak to the cardinal extremities; in the median 

 portion of the valve the surface is flattened along an indefinite band 

 extending from the umbonal region to the front, and is sometimes de- 

 pressed to form a shallow, ill-defined median sinus; the surface of the 

 valve is marked by from 19 to 21 simple, depressed, rounded plications 

 which increase gradually in size in passing from the beak to the margin, 

 sometimes a plication much narrower than those on either side is inter- 

 calated along the median line at near the mid-length of the shell, and 

 continues to the front margin. 



Brachial valve less convex than the pedicle, the greatest convexity 

 posterior to the middle, the beak extending a little beyond the hinge-line 

 posteriorly, the surface curving abruptly from the umbonal region to the 

 cardinal and postero-lateral margins, the median portion sometimes a 

 little flattened along an indefinite band extending from the middle cf 

 the shell to the anterior margin, but never elevated into a distinct mesial 

 fold; the surface marked by plications similar in form and number to 

 those of the opposite valve. 



