550 Systematic Paleontology — Upper Devoxlvx 



beneath umbo. Posterior muscular scars more widely separated, indis- 

 tinct in cast observed. Large C-sliaped vascular markings near margin. 

 Exterior not observed. Shell substance punctate. 



Width 16 mm.; length (antero-posterior diameter) 12 mm.; height 

 7 mm. 



The cast of the interior of a single valve has been oliserved. While 

 unusually convex it agi'ees with tins species in other respects. The C- 

 shaped markings of the vascular sinus, characteristic of the genus Crani- 

 ella, are observable upon the cast though not shown in the drawing. 



Occurrence. — Jennings Formation, Parkiiead Member. Williams 

 Eoad, Polish Mountain, 1660. 



Collection. — Maryland Geological Survey. 



Craniella ? sp. 



Description.- — Shell low conical, subcircular or slightly transverse. 

 Umbo excentric, near posterior margin. Dorsal valve quite convex from 

 umbo to anterior margin, less so to lateral margin, slightly concave to 

 posterior margin. Height of valve variable, about one-fourth diameter or 

 less. Interior of valve shows a pair of indistinct scars beneath umbo for 

 attachment of anterior adductor muscles. Shell substance punctate. 

 Ventral valve not observed. 



Diameter 15 to 20 mm.; height 3 to 4 mm. 



The identification of these specimens is not assured, the interior not 

 being sufficiently well preserved to permit of confident generic determina- 

 tion. It is not improbable that the species is C. hamiltonice though much 

 less convex than the other ]\Iaryland individuals referred to that species. 



Occurrence. — Jennings Formation, Chemung Member. EUerslie, 

 Pennsylvania, 1474, 1508. 



Collection. — Maryland Geological Survey. 



Genus CRANIA Retz 



Crania sp. 

 Desaipiion. — A single dorsal or upper valve of this genus has been 

 observed and is insufficient for specific identification. The genus is like- 

 wise but sparingly represented in the Chemung fauna elsewhere. 



