Rathbun.] 30 [May 15, 



valve. It is regularly rounded from side to side, but on the anterior 

 half it is marked with two longitudinal, shallow and narrow, but de- 

 fined depressions, giving it there a three-lobed character. In one 

 specimen the central lobe is slightly broader than the laterals; in an- 

 other the central lobe is the narrower. On each side of the fold are 

 eight simple, rounded plications, separated by slightly narrower, 

 rounded depressions, the plications growing successively smaller in 

 size toward the sides, and the more lateral ones bending slightly out- 

 ward as they extend from the binge line toward the margin. The 

 plications are not very distinctly marked on the posterior part of the 

 valve. Only two dorsal valves of this species are known. The larger 

 is imperfect, but the smaller has the following dimensions; length 

 21 mm., breadth 33 mm., depth of dorsal valve 5.5 mm. Ventral 

 valve unknown. 



This species of Spirifera is readily distinguished by the three-lobed 

 character of the dorsal median fold. In all of the other Devonian 

 species from Brazil, the median fold is simple. 



Devonian sandstone, Rio Mtecurii. (Geol. Comm., 1876.) 

 Spirifera msecuruensis, sp. nov. 



Shell minute, gibbous, with rounded cardinal extremities, and 

 about four low, broad, rounded plications on the ventral valve. 



Ventral valve very convex; length and breadth about equal; in 

 outline forming obliquely a nearly square figure, but with the ante- 

 rior margin of the shell slightly rounded. The surface arches strongly 

 upward from the front, along the median line, to a point a short dis- 

 tance back of the middle of the valve, whence it curves slightly 

 downward to the beak. Beak large and prominent, and much ex- 

 tended behind the hinge line, but only slightly incurved. Hinge 

 area broad, triangular and very slightly concave; inclining strongly 

 forward from the beak, so as to form an angle of about 110° to 120° 

 with the plane of the shell margins. The distance from the hinge 

 line to the beak is equal to nearly one-third the entire length of the 

 valve, and in the triangular figure formed by the hinge area, the base, 

 represented by the hinge line, is equal to about one and one-half 

 times the length of each of the other two sides. Cardinal margins 

 not sharply defined, the surface curving rapidly over from the hinge 

 area into the general surface of the valve. Length of the hinge line 

 equal to nearly two-thirds the width of the valve; cardinal extremi- 

 ties regularly rounded ; fissure large, triangular, but widening only 

 gradually from the beak toward the hinge line, where its width is 



