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in shale, except at the posterior extremity where the 

 actual bone is present for a length of 1 1 mm. In form 

 this mandible agrees well with that of the type species, 

 Selenosteus brevis, but is only about half its size. The 

 bone is very thin and bears fine striations similar to 



Fig. 26. Sdenosteus sp. X i§. Rhinestreet Shale (Portage); Eighteen 



Mile Creek, N. Y. 



a, Left mandible. — E 2393. b, left mandible. — E 2394. c, dorsomedian. — 

 E 2396. 



those of the type species. Length, as far as preserved, 

 43 mm. 



Rhinestreet shale (Portage); from Eighteen Mile 

 Creek, near Hamburg, Erie County, N. Y. Collected 

 by W. L. Bryant. 



