Maryland Geological Survey 317 



are ratlier large and divergent and are free from impressions of papilla?. 

 In the interior of the brachial valve a low median ridge reaches more than 

 half way to the front of the shell. 



" The dimensions of a medium-sized specimen are: Length, 28 mm.; 

 breadth, 30 mm." Weller, 1903. 



This species is the same as Stropheodonta hipartita which Weller de- 

 scribes from the Decker Ferry of New Jersey and which he considers the 

 same as the three shells described by Hall in Volume II of the Pale- 

 ontology of New York under the names Leptcena sp., Leptcena hipartita, 

 and Stropheodonta textilis, all from the Coralline limestone of Schoharie, 

 New York. It differs from the three forms described by Hall in having 

 the striae curve outwards on the sides of the shell in approaching the 

 margins, the curvature increasing towards the posterior portion of the 

 shell. This curvature is not mentioned in Hall's description and on ex- 

 amining the type material the strijp do not curve but radiate from the beak 

 straight. While this form is the same as that described by Weller it may 

 prove to be a distinct species from Hall's. 



It is distinguished from S. planulaia of the Lower Helderberg by the 

 curvature of the alternating angular striae, while the striae of S. planuJata 

 are fine and even. 



Occurrence. — Hklderbeko Formation, Keyser Member. Devil's 

 Backbone, Hancock, Cookerly, i;; miles northeast of Flintstone, Pinto, 

 Maryland; Hyndman, Pennsylvania. 



Collection. — Maryland Ecological Survey. 



[Maynard.] 



Stropheodonta ( Leptostropiiia) auctimuscula n. sp. 

 Plate LVIII, Fig. 1 

 Desmption. — This is a very flat species of Stropheodonta, with the 

 ventral muscle area very much narrower and more excavated than in other 

 forms from the Oriskany. The striae are somewhat coarser than in S. mag- 

 nifica, there being about twelve in 5 mm., while in the latter there are from 

 fifteen to twenty in the same space in Cumberland specimens. L. orisJcania 

 Clarke,' with which it was at first identified, is a somewhat smaller species, 



' Mem. N. Y. State Mus., voL iv, No. 3, 1900, p. 53, pi. vii, figs. 29-35. 



