MARYLAND GEOLOGICAL SURVEY 321 



25. The sides slightly convex, the angles furrowed. Each side marked 

 by a series of angular, transverse costae, which are directed obliquely 

 forward toward the aperture from each lateral margin forming a rounded 

 angle of about 130 at the median line; from two to four of these costae 

 occupy the space of 1 mm., being closer together and finer near the apex 

 of the shell and becoming progressively coarser towards the aperture. 

 The furrows between the costae are wider than the ridges, rounded in the 

 bottom, and are crossed at right angles by fine raised bars joining adjacent 

 costae, which are somewhat closer together than the costae themselves and 

 not quite as high. 



" The dimensions of a specimen which is somewhat incomplete at the 

 apex are : Length, 38 mm. ; diameter at aperture, 18 mm." Weller, 1903. 



Occurrence. MARTINSBURG SHALE (Sinuites bed). Five miles south- 

 west of Chambersburg, Pennsylvania, and at Strasburg, Virginia. Treii- 

 ton limestone of New York. 



Collection. U. S. National Museum. 



CLASS CEPHALOPODA 

 subclass TETRABRANCHIATA 



Order NAUTILOIDEA ;,;'., 4 J:S 

 Suborder HOLOCHOANITES 

 Family ENDOCERATIDAE 

 Genus CAMEROGERAS Conrad 



CAMEROCERAS sp. 

 Plate XXXVII, Fig. 10 



Description. The thin slabs of Frederick limestone not infrequently 

 exhibit subcylindrical bodies now composed of crystalline matter, which 

 are supposed to represent the endosiphuncle of some species of Carrier o- 

 ceras. With no other evidence it is impossible to identify the species of 

 this cephalopod. 



