128 Carl 0. Dunbar, 



exceedingly fine concentric lines, of which twenty-five to thirty 

 occupy a space of 2 mm. Occasionally one of the major striae 

 disappears before reaching the edge of the shell, in which case 

 one of the nearby secondary striae at once becomes stronger to 

 take its place. 



Dimensions of an imperfect specimen: Length, about 40 mm.; 

 width, about 50 mm. 



Discussion: In the Linden formation of Tennessee, S. punc- 

 tulifera has a tendency to fail to normally increase its striae with 

 growth. For this reason the specimen described is retained as a 

 variety of that highly variable species. In the rather extensive 

 collection made by the writer, however, no closely connecting 

 forms were found to link this new variety to that species. The 

 shell most closely resembles vS". williamsi of the Niagaran, which 

 is a much smaller species with more distinct secondary striae. 



Occurrence: Birdsong shale, on Sycamore Creek, near Hol- 

 laday. 



Name: The variety is named for Mr. John Holladay, to whom 

 the writer is indebted for information and fossils from the Syca- 

 more Creek localities. 



Strophonella lineolata, n. sp. 

 Plate II, figs. 20, 21 



Description: Outline semi-elliptical, the length varying 

 between three-fourths and four-fifths the width, the hinge-line 

 usually a little less than the greatest width below. Ventral valve 

 slightly convex in the umbonal region, and evenly concave over 

 the lateral and anterior portions ; the dorsal valve conforming 

 in contour, slightly concave near the umbo, and gently convex 

 to the margin but not geniculate. The depth of curvature of the 

 shell equals about one-fourth of its lateral width. 



The surface is covered with narrow, sharp striations. sepa- 

 rated by concave interspaces that are about twice as wide as 

 the striae. The striae increase by intercalation and average about 

 seven in a space of 5 mm. on the middle portion, but usually 

 become finer and more numerous near the anterior margin, where 

 about ten occupy a space of 5 mm. 



Dimensions : Width, 44 mm. ; length, 35 mm. 



