MARCELLUS LIMESTONES OF LANCASTER 157 



BRACHIOPODA 



schizobolus Ulricli 

 Schizobolus truncatus (Hall) 



Pal. N. Y. 4:23, pi. 1,2 



This species is represented by one shell from bed III. It is a 

 fairly well preserved interior of a brachial valve with median 

 septum, and muscular scars. The lowest horizons at which this 

 species has been previously recorded is the upper Hamilton (Mos- 

 cow) shales. Its occurrence at this lower level is of interest. 



crania Retzius 

 Crania crenistriata Hall 



Pal. N. Y. 4:28, pi. 3 



One specimen has been found in bed VII, attached to O rt h o- 

 c e r a s m a r c e 1 1 e n s e . 



Crania recta 1 sp. nov. 

 PI. 9, fig. 1-3 



The three specimens obtained are all upper valves. Two 

 are molds of the external surface with minute fragments of the 

 posterior portion of the shell retained; the third shows the 

 exterior. The former were attached to the interior and the latter 

 to the exterior of the living chamber of Orthoceras. 



Upper valve transverse, having the form 'of a flattened rim 

 with sharply elevated central portion; beak subeentral. A shal- 

 low sinus, widening toward the front, extends from the beak to 

 the anterior margin. Outline of the valve straight on the 

 posterior side, regularly rounded at the sides, and slightly 

 arcuate in front. Surface marked by fine lines of growth. 

 Under a strong magnifier the surface is seen to be minutely 

 granulose, a feature not visible under an ordinary hand lens. Pos- 

 terior adductor scars are shown on a fragment of shell remaining. 



Lower valve unknown. 



The characteristic features of the species are the straight pos- 

 terior margin and greater transverse diameter. 



1 Acknowledgments are due to Charles Schuchert, for comparing these shells with other species 

 of the genus. 



