PALEONTOLOGY. 421 



MOLLUSCOIDEA. 



BRACHIOPODA. 



Genus STREPTORHYNCHUS King. 



Streptorhynchus flabellum. 



PLATE II, figs. 7 and 9. 

 Streptorhynchus flabellum Whitf., Ann. N. Y. Acad. Sci., March, 1882, p. 200. 



Shell below a medium size, semi-circular or semi-ovate in outline, with a 

 straight hinge-line of variable length; the lateral and front margins are somewhat 

 regularly rounded and, in a profile view, irregularly bi-convex. Ventral valve 

 depressed convex, with a more or less elevated and projecting but twisted or dis- 

 torted beak, overhanging a nearly vertical cardinal area of irregular form and width, 

 which is divided in the middle by a narrowly triangular convex deltidium. The 

 dorsal valve is almost regularly semi-circular, very depressed convex, with a slightly 

 more prominent umbo, and is destitute of cardinal area. Surface of the valves 

 marked by from twenty-two to twenty-four strong, rather sharply elevated, radiat- 

 ing plications, which are entirely simple, and separated by broad, concave inter- 

 spaces. The shell is also further marked by fine, regular, concentric striae of 

 growth, which arch backward in crossing the radii, and may have been sub-lamellose 

 on the external surface, but the examples seen are all exfoliated. 



The species is of a somewhat unusual type, especially in Devonian 

 rocks. The dorsal valve seen alone presents so much the appearance of 

 a strongly-marked Aviculopecten, that when first observed it was thought 

 to belong to that genus; but the ventral valve, similarly marked, and 

 possessing the characteristically twisted cardinal area and beak with its 

 covered fissure, at once indicates its true position. It is entirely unlike 

 any species hitherto described from American rocks, and will not easily be 

 mistaken. It resembles, in the features of the dorsal valve, specimens of 

 Orthis flabellum from the shales of the Niagara group of New York and 

 elsewhere; but it is more coarsely marked, with wider and more deeply 

 concave interspaces. 



Formation and Locality. — In the limestone of the Upper Helder- 

 berg group, at Smith and Price's quarries, near Columbus, Ohio. Col- 

 lected by Mr. Hyatt. 



Genus RHYNCHONELLA Fischer. 



Rhynchonella f raricosta. 



Plate II, fig. 6. 

 Rhynchonella raricosta Whitf, Ann. N. Y. Acad. Sci., March, 1882, p. 201. 



Shell of moderate size, and somewhat transversely sub-triangular in outline, 

 when seen upon the ventral side. Ventral valve flattened and very shallow, with a 

 short, obtuse, and not at all incurved beak ; cardinal slopes incurved, and the mar- 

 gins straight from the beak to near the point of greatest width of the valve, 

 the angles of divergence being nearly or quite 120 degrees. Front of the valve 

 broadly curved, and marked by several deep indentations corresponding to the 

 number of plications marking the surface. Middle of the valve marked by a broad, 

 shallow, slightly angular mesial sinus, which is more than one-third as wide at the 



