326 Systematic Paleontology 



the Hall collection, that cannot be distingnished from this species. Here, 

 therefore, are forms transitional to S. ainpla of the Onondaga. The ex- 

 terior in these two specimens is not preserved, and no positive identifica- 

 tion can be made, though they seem to be ^S'. headleyana. 



Occurrence. — Helderberg Formation, New Scotland Member. 

 Corriganville. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



Stropiionella undaplicata n. sp. 

 Plate LIX, Figs. 13, U 



Description. — Shell large, concavo-convex, resupinate, semioval to sub- 

 semicircular; length two-thirds to three-fourths width, hinge-line equal- 

 ling or slightly greater than greatest width, extremities slightly extended. 

 Ventral valve convex anteriorly, umbo concave, area not observed. Dorsal 

 valve concave anteriorly, umbo convex. Surface ornamented by coarse, 

 irregular, sinuous plications which may unite again forming elliptical de- 

 pressions between them. Plications increasing by bifurcation or inter- 

 calation, more numerous and finer towards margin. Interior not observed. 



Length of large individual 4.5 cm. ; width 5.2 cm. Other specimens 

 are shorter proportionally. 



This species closely resembles S. headleijana to which it was earlier 

 referred. Its ornamentation is distinctive. 



Occurrence. — Helderberg Formation, New Scotland Member. 

 Dawson, Corriganville. 



Collection. — Maryland Geological Survey. 



[Swartz.] 



Genus SCHUCHERTELLA Girty ' 



The specific characters of these shells are about as variable as is the 



generic name under which they have been grouped. For a long time they 



were referred to the genus Streptorhynchus. In 1884 Waagen showed that 



the interior generic characters were different, and thinking he had cor- 



' Orthothetes of authors. For a diagnosis, see Hall and Clarke, 1892, Nat. 

 Hist. N. Y., Pal., vol. viii, pt. i, p. 253, and Girty, 1904, Proc. U. S. Nat. Mus., 

 vol. xxvii, p. 734. 



