236 



XXIII. On the Devonian Brachiopoda of Erere', 

 Province of Para', Brazil 



BY EICHARD EATHBUJST, 

 Of the Geological Laboratory, Cornell University. 



[Read before tlus Society January 2d, 1874.] 



Terebratula Derbyana, Hartt, sp. nov., Plate X, figs. 15, 17, 18, 19, 20, 21, 



23, 24 and 25. 



Test small, generally subovate in outline, but sometimes subangular poste- 

 riorly, lenticular, with nearly equally convex and somewhat flattened valves. 

 Breadth usually about three-fourths, though sometimes nearly equal to, the 

 length, and greatest at or anterior to the middle. Surface smooth. 



Ventral valve depressed-convex, with the greatest convexity posterior to the 

 middle. The beak appears to be more or less pointed, slightly extended 

 beyond the dorsal valve and incurved, with quite a broad deltidium beneath ; 

 but the external moulds, owing to the friable character of the sandstone in 

 which they were taken, are all more or less defective in the umbonal region. 

 The posterior lateral margins, diverging from the beak at an angle a little 

 greater or less than a right angle, and slightly rounded or nearly straight, ex- 

 tend forward nearly half the length of the valve, when they bend gradually to 

 unite with the lateral margins, which, together with the front, form a single 

 regular curve. 



Dorsal valve generally slightly elongate, but sometimes nearly circular in 

 outline, depressed-convex like the opposite valve, the convexity strongest pos- 

 teriorly, the curve from the beak to the front being very gentle. 



The surface of both valves is smooth, though sometimes it is traversed by 

 several more or less prominent concentric lines of growth. 



There is neither fold nor sinus, and altogether the test presents a very plain 

 appearance. 



Length, 10 m. m., breadth, 7.5 m. m., thickness, 3 m. m. 



This species occurs quite abundantly in the Devonian sandstone 

 of Erere, associated with Strejytoi'liynclius Agassizii, Vitulina jmstu- 

 losa, etc. Many specimens of different ages are often found crowded 

 together in a small space in the friable portions of the sandstone, 

 and preserved in the form of external and internal moulds. 



