26 NEW YORK STATE MUSEUM 



Pterinopecten cf. proteus Clarke and wulfi Freeh 



Plate 3, figure i 



Pterinopecten proteus Clarke. N. Y. State Mus. Mem. 3. 1900. p. 32, pi. 4, 



fig. 4-8 ; and 

 Pterinopecten wulfi Freeh. Devon. Aviculiden Deutschlands, p. 25, pi. 2, fig. 7 



The small specimen figured here under enlargement is compared with 

 the species above cited from the Becraft Mountain Oriskany of New York 

 and the Lower Coblentzian of the Eifel. 



Horizon. No. 10. 



Pterinea intercostata Clarke 



Plate 3, figures 8-12 



Pterinea intercostata Clarke. N. Y. State Mus. Bui. 107. 1907. p. 206 



Shell suberect or oblique with small auricle and well defined, broad but 

 not extended posterior ear. Hinge straight, about two thirds the greatest 

 diameter of the shell. Beaks anterior, subterminal. Left valve with coarse 

 and strong radial ribs separated by broad flat interspaces. Of these one 

 can count about 12 on the body of the shell. The primary interspaces are 

 usually divided by a much finer median riblet but further subdivision is 

 very unusual. On the broad posterior wing radial ribs are sparse and indis- 

 tinct though usually traces of them may be seen. Here the fine concentric 

 lines predominate, giving the surface a smoothness in contrast to the rest 

 of the valve. The concentric lines are also visible on the rest of the surface. 

 As usually preserved they make faint interruptions of the radial ribs but 

 when normal are lamellose and strongly defined. The right valve is prac- 

 tically devoid of radial sculpture, the surface being crossed by sharply 

 defined concentric lines, only the posterior wing showing a few riblets on 

 the cast. The contrast in the markings of the two valves is extreme but is 

 conclusively demonstrated by several specimens with both valves retained. 



This species may be compared in respect to ornament with several 

 coarsely ribbed shells, e. g. P. costata Goldfs., Avicula rigoma- 

 gensis Freeh, from the Coblentzian, A. reticulata Sowerby, from 

 the Aymestry limestone, but such comparisons are resemblances only in 

 one or another feature. No closely allied form is now recognized. 



Horizon. No. 9. 



Pterinea cf. pseudolaevis OEhlert 



Plate z, figures 2, 3 



This is a smooth-shelled species of suberect form with evenly convex, 

 subcircular lower margin, broad but not extended or deeply concave pos- 

 terior wing. The body of the left valve is not highly convex nor promi- 

 nently set off from the posterior wing to which it slopes quite gently. The 



