1918] The Ottawa Naturalist. 121 



THE RICHMOND FAUNAS OF LITTLE BAY DE 

 NOQUETTE, IN NORTHERN MICHIGAN. 



By A. F. Foerste. 



(Continued from page 103). 



Pterinea (Caritodens) demissa (Conrad) is represented by 

 specimens 50 millimeters in height, both in the cherty Richmond and 

 in the upper part of the underlying argillaceous Richmond. At both 

 horizons it is associated with a Byssonychia which is similar to the 

 form occurring more or less abundantly in the Waynesville member 

 of the Richmond on Manitoulin Island, in Ontario, but good speci- 

 mens for figuring are rare. 



The Opisthoptera occurring in the cherty Richmond bears a gen- 

 eral resemblance to Opisthoptera casei (Meek and Worthen) but 

 probably is a distinct species. Anteriorly, along the umbonal ridge, 

 the shell is convex and elevated above the more posterior parts of the 

 shell very much as in Byssonychia, and this appearance is strengthened 

 here by a tendency of the radiating plications here to remain simple. 

 Moreover, the anterior outline of the shell is concavely curved near the 

 beak and convexly curved below, more as in Byssonychia than in 

 typical Opisthoptera casei. Along the posterior part of the middle third 

 of the shell, posterior to the umbonal part, the plications are arranged 

 in fasciculate groups, while along the posterior third and also along 

 the anterior margin the plications tend to be narrow, numerous, and 

 subequal. This probably is a new species, but no specimens suitable 

 for figuring have been found so far. 



Clionychia angusta sp. now, Fig. 20. This species has been 

 figured so as to suggest a form similar to Clionychia excavata Ulrich 

 (Geol. Surv. Ohio, vol. 7, 1893, pi. 51, figs. 4, 5), from the White- 

 water member of the Richmond in Indiana. As a matter of fact, how- 

 ever, the specimens at hand do not show any indication of a ligamental 

 area along the upper part of the shell when thus oriented. Compared 

 with the Indiana species, when thus oriented, the shell is narrower 

 and the basal part is more abruptly rounded. It occurs in the cherty 

 Richmond, associated with specimens of Cymatonota resembling 

 Cymatonota typicalis Ulrich but not sufficiently preserved to make 

 their identity certain. Small modiolopsoid specimens resembling 

 Colpomya faba (Emmons) also occur. 



Ten feet below the base of the cherty Richmond there is an 

 argillaceous band, 12 to 18 inches in thickness, forming a single layer, 

 usually spalling off in larger masses than the immediately overlying 

 or underlying strata; in this layer fossils, with the exception of certain 

 lamellibranchiata, are few. This is the chief horizon for 



