272 



A full synonymy of American specimens of this widely distributed 

 species, with references, is given on page 240 of Mr. Charles Schuchert's 

 " Synopsis of American Fossil Braehiopoda," published at Washington, 

 in 1897, as Bulletin No. 87 of the United States Geological Survey. 



Orthis, sp. indet. 



From an exposure ten miles above the mouth of the river ; a cast of the 

 interior of a ventral valve of a coarse-ribbed species. 



CamAROTCECHIA (1) WiNISKENSIS (N. Sp.) 



Plate 25, figs. 5 & 6. 



Shell compressed, broadly rounded in front, obtusely angular behind, 

 the larger specimens somewhat pentagonal in marginal outline and a little 

 wider than long, the smaller ones ovately subcircular or widely subovate, 

 and a little longer than wide ; front margin of the valves shallowly 

 sinuate. 



Ventral valve with a rather obscurely defined shallow median depres- 

 sion, that is obsolete or undeveloped in young specimens, marginal in 

 older ones, and that extends backward to a little beyond the midlength 

 in full grown ones; a nearly straight, rather prominent or produced umbo, 

 and an acute and very slightly incurved beak. 



Dorsal valve (of apparently not quite mature individuals) uniformly 

 compressed convex and moderately inflated, its umbo and beak much 

 smaller than those of the ventral. 



Surface of both valves marked with numerous, closely disposed and 

 very narrow radiating ribs, with fine grooves between them. In the 

 largest specimen collected, a detached ventral valve some fifteen milli- 

 metres wide by twelve mm. and a half long, there are six ribs in the sinus, 

 and fourteen or fifteen on each side. 



Hinge area and characters of the interior of the valves unknown. 



The foregoing description is based upon three detached ventral valves, 

 that are a little wider than long, and upon two smaller specimens, with 

 both valves, that are a little longer than wide, all from an exposure thirty- 

 four miles above the mouth of the river ; but one small specimen from an 

 exposure ten miles above the mouth of the river, is also probably refer- 

 able to this species. 



CamAROTCECHIA (?) COALESCENS. (N. Sp.) 



Plate 25, fig. 7. 



Shell very small, moderately convex, subovate in marginal outline and 

 a little longer than wide, with a shallow sinus or depression at and near 



