New Species of Devonian Fossils. 127 



shell below. Dorsal valve conforming in contour to the ventral. 

 Surface marked by fine striae, about twelve of which occupy a 

 width of 5 mm. The striae are low and rounded and separated 

 by rounded interspaces. They increase rapidly by bifurcation 

 on the dorsal valve, while both bifurcation and intercalation were 

 observed on the ventral valves, the latter predominating. The 

 striae are crossed by very fine concentric lines. When slightly 

 exfoliated, the shell appears almost smooth, only darker translu- 

 cent lines marking the former position of the strife. Shell sub- 

 stance finely punctate. Cardinal area narrow and mostly confined 

 to the ventral valve. Denticulations extending only about half 

 way from the beak to the cardinal extremities, about twenty 

 denticulations in a distance of 5 mm. On the ventral valve the 

 muscle-scars are very lightly impressed, consisting of narrow 

 flabelliform diductors, embracing the narrow adductors, which 

 are close up under the beak. 



Dimensions: Length, 32 mm. ; width, 40 mm. ; depth of con- 

 vexity. 10 mm. 



Occurrence: Abundant in the Birdsong shale at the "steel 

 bridge" on Big Sandy River, at numerous localities on Birdsong 

 and Big Lick creeks, and at Perryville. Also occurs in the Olive 

 Hill formation at Olive Hill, Grandview, and elsewhere. 



Name: Species name given in honor of Doctor A. H. Purdue, 

 late state geologist of Tennessee. 



Strophonella punctulifera holladayi, n. var. 

 Plate H, figs. 18, 19 

 Description: Shell having the general shape and contour of 

 6*. punctulifera. Surface marked by a few fine and widely 

 spaced striations, between which are nearly flat interspaces cov- 

 ered with much finer, subdued striae. The larger striations are 

 sharp and threadlike, less than 0.5 mm. across, and equally as 

 high. They increase by intercalation, in the umbonal region 

 only, so that the interspaces increase in width to an average of 

 3 mm. at the anterior margin. About thirty of these strong 

 striae may be counted around the edge of the shell. The obscure 

 secondary striae, of which ten to twelve occupy a space of 2 mm., 

 are barely visible to the eye. The whole surface is covered by 



