1878.] 21 [Rathbun. 



able that we have more than a single species included in Chonetes 

 Herbert- Smilhii, as originally founded. Much of the material at 

 hand is in an imperfect state of preservation, the majority of the 

 specimens, however, belonging to the type as first described. Thus it 

 does not seem advisable to make a division of the species, until other 

 and better material has been obtained. 



Moderately abundant in the Devonian sandstone of Erere. (Mor- 

 gan Exs., 1870 and 71; Geol. Comm., 1876.) 

 Chonetes curuaensis, sp. nov. 



Shell small and transverse, with the proportions of length to 

 breadth about as 2 to 3 ; in outUne longitudinally sub-semielliptical, 

 the lateral margins being nearly straight posteriorly, and not curving 

 much, excepting toward the front. Hinge line straight and nearly or 

 quite as long as the width of the shell, which has the cardinal ex- 

 tremities forming right angles or, probably, slightly rounded. 



Ventral valve gently convex and most elevated near the middle, 

 but having the convexity slightly more pronounced on the umbonal 

 region than toward the front of the valve. Curve along the trans- 

 verse diameter gentle and nearly regular, though the sides of the valve 

 appear to slope from the median line to the lateral margins with little 

 curvature. Cardinal extremities flattened. Beak small, but dis- 

 tinctly marked, slightly depressed and projecting only a short dis- 

 tance behind the hinge line. There is a small, well-defined septum, 

 extending forward from the beak a little more than one-fourth the 

 shell length. Hinge area and spines not preserved. Surface 

 marked with fine, but prominent, subangular, radiating raised lines, 

 which are slightly narrower than the intervening depressions. 

 There are about twenty-six of these lines on one ventral valve, on 

 which, however, the cardinal extremities are smooth; there also exist 

 one or two rather prominent, concentric lines of growth. Length of 

 valve about 6 mm., breadth 9 mm. Dorsal valve unknown. 



This species of Chonetes, which is represented by only a single 

 perfect specimen, bears some resemblance to C. Herbert- Smithii of 

 the Erere locality, from which, however, it differs in the fact that the 

 ventral valve of the former is less strongly convex, and has a more 

 prominent beak and finer surface markings. It also resembles some- 

 what the young of C. Freitasii of the Rio Mascurii locality. From 

 C. scilula Hall, of the Hamilton group of New York State, which 

 it resenibles much in form, it differs in having fewer and coarser 

 raised lines. Only a few specimens of this species have been found. 



