Contributions to Invertebrate Palaeontology. 521 



space in each polyp, and by the strongly developed transverse 

 tabuljE ; also by the rays not extending to the centre, as in that 

 species and in those of the genus Acervularia. When the coral is 

 weathered, or the substance becomes chalky, so that the polyps are 

 readily separable from each other longitudinally, the appearance 

 very closely resembles that of Gyathophyllmn rugosum when in a 

 similar condition, but the interruption of the rays before reaching 

 the centre, and the great extent of the tabulae, will then serve to 

 distinguish them. 



Formation and Locality. — In the Upper Helderberg group, in 

 Paulding County, Ohio. 



MOLLUSCOIDEA. 



BRACHIOPODA. 



Genus STREPTORHYJVCIIIJS King. 



Streptorliyncliiis flal)elliiiii. 



Plate VI, figs. 7 and 9. 



Streptorhynchus Jlahelhmi Wliitf., 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 some- 

 what 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 distorted 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, radiating plications, which are entirely simple, and 

 separated by broad, concave interspaces. 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 appear- 

 ance 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 car- 

 dinal area and beak with its covered fissure, at once indicates its 

 true position. It is entirely unlike any species hitherto described 

 AnxNAls N. Y. Acad. Sci., V, Dec. 1890.— 35 



