Trematis Dyeri — Beyrichia Richardsoni. 347 



The range of the three species of Lichenocrinus, thus far described in 

 the Cincinnati Group, may be characterized, so far as known, as follows : 

 the cvateriformis, from low water-mark to 300 feet above ; Dyeri, from 

 200 to 500 feet above ; tubereulatits, if it should include the Clarksville 

 specimens, from 500 to 800 feet above, but if the Clarksville specimens 

 belong to a distinct species, then the tuberculatus must be confined to the 

 upper 200 feet or less of the group. 



Trematis Dijeri — (S. A. Miller). 



Fig. ^9— Trematis Dyeri. Imperforated valve, enlarged about two diameters. 



Shell elongate, subovate ; valves unequally convex ; upper or im- 

 perforated valve strongly convex ; umbo projecting slightly beyond 

 the margin ; surface marked with twenty or more distinctly elevated, 

 regular, concentric lamellse, giving the valve a rough appearance. No 

 punctations have been observed upon this valve, and no radiating 

 strife are visible upon the exterior or interior side. Lower or ventral 

 valve slightly convex ; umbo subcentral ; surface punctate, and 

 marked with concentric lines ; oval slit, for the passage of the pedicle 

 fibers of attachment, narrow, and situate between the umbo and pro- 

 jecting beak of the opposite valve. 



Hinge and internal structure unknown. Length of specimen |th 

 inch, and greatest breadth about -j^ths inch less. 



The specimen engraved is from the collection of C. B. Dyer, Esq., 

 in whose honor I have given the specific name. He found it on the 

 hill back of Cincinnati, but its range is unknown. It is an extremely 

 rare fossil. 



Beyrichia Bichardsoni — (S. A. Miller). 



Fig. 40— Beyrichia Bichardsoni. Magnified 6J^ diameters. 



Shell small, somewhat rectangular, rounded at each end, and trun- 

 cated obliquely at the dorsal angles ; narrow border on the ends and 



