Morgan Expeditions. 123 



Although only a single specimen of this species, which 

 has been referred with some doubt to Edmondia, has been 

 obtained, and that is not a very perfect one, it has been pos- 

 sible from it to make out the principal characters of the 

 species quite accurately. It is readily distinguished from 

 all the other species of lamellibranchs yet found at Erere, 

 by the nearly symmetrical valves and sub-central beaks. 



From the Devonian sandstone, Erere, Prov. of Para, 

 Brazil, with Spirifera Pedroana, etc. 



[Named in honor of my friend, Senhor Jose Gualdino da 

 Silva, of Para, to whom I am under many obligations. C. 

 F. H.] 



Genus MODIOMORPHA, Hall. 



Modiomorpha Pimentana, sp. nov. 



Shell of moderate size, elongate, sub-quadrilateral in outline. From 

 the beaks, which are placed at less than one-fourth the length from the 

 front, the height increases very gradually to the posterior end of the 

 hinge margin, which last equals about three-fifths the length of the shell 

 and is straight ; height of shell at beak about five-sixths that at end of 

 hinge margin. Anterior margin straight and oblique for about one-half 

 its length, forming at the beak an angle of about 135° with the dorsal 

 margin. It rounds abruptly to the ventral margin, which, in its posterior 

 three-fourths, is nearly straight. The posterior margin is slightly con- 

 vex, and extends obliquely backward from the dorsal margin, with which 

 it forms an angle equal to about that at the beaks, and curves abruptly to 

 the ventral margin. Beaks very small, obtuse and not produced above 

 the hinge line. The valves are quite convex, the surface rising rapidly 

 from the ventral and anterior margins on the one side, and from the 

 dorsal and posterior margins on the other, toward a line running obliquely 

 across the valves from the beaks to the lower posterior extremity. Along 

 this line the valves are sometimes angular, at others they are regularly 

 and strongly rounded ; generally, however, they are angular near the 

 beaks and become gradually rounded and flattened posteriorly. Above, 

 the surface slopes to the dorsal margin very abruptly and is concave just 

 behind the beaks, but the slope becomes more and more gradual toward 

 the posterior extremity, and, from very slightly concave at first, it changes 

 to very slightly convex posteriorly. The lower and anterior portion of 

 the valves is sometimes broadly flattened. Surface marked with numer- 

 ous concentric lines of growth. Length, 30 mm ; height, 16 mm ; depth of 

 single valve, 5 ram . These dimensions are of the largest specimen found; 

 most of the specimens are much smaller. 



