New Species of Devonian Fossils. 131 



Chonetes hudsonicus camdenensis, n. mut. 

 Plate II. fig. 17 



Description: Shell of medium size, almost semi-circular in 

 outline. Greatest width at the hinge-line, beneath which the 

 lateral margins are very slightly contracted and then round 

 evenly into the nearly transverse anterior margin. Pedicle valve 

 varying from nearly flat to gently and evenly convex, except 

 where slightly flattened toward the cardinal extremities. Its 

 cardinal margin commonly shows one short spine near the car- 

 dinal extremity, directed outward at an angle of 50° or 60° from 

 the beak. There are indications of two pairs of smaller spines 

 nearer the beak. Surface covered by very fine radiating striae 

 of which about twenty occupy a space of 5 mm. Striae increas- 

 ing by both intercalation and bifurcation. 



Diiiiciisions of an az'cragc specimen: Length, 12 mm.; width, 

 19 mm. ; convexity, 2.5 mm. 



Discussion: This shell closely resembles C. hudsonicus of the 

 Oriskany. It averages fully one-half larger, however, and does 

 not show any sign of a ventral sinus such as the New York form 

 possesses. 



Occurrence: Rare in the Plarriman novaculite and common in 

 the Camden chert at many localities in Benton County. 



FAMILY PEXTAMERID.E 



Gypidula multicostata, n. sp. 

 Plate III, figs. 12, 13 



Description: Shell subtrigonal in outline. Ventral valve 

 strongly convex and much larger than the dorsal. Its beak 

 narrow and strongly arched, but not incurved over that of the 

 opposite valve. The sides diverge regularly to their greatest 

 width at about three-fourths to four-fifths the distance to the 

 front of the shell, then round abruptly into the broad and very 

 slightly emarginate anterior margin, so that the outline is almost 

 an isosceles triangle. Dorsal valve transversely elliptical and 

 gently convex. A broad but low flat fold occupies the median 

 half of the ventral valve, becoming obsolete before reaching the 

 beak, and a corresponding sinus is present on the dorsal valve. 

 The fold and sinus bear each ten to twelve slender, sharp, angu- 



