•24:4: 



Found four feet l)elow the base of the Trilobite beds, in 

 Avery's Creek ( rare ) ; and very rarely in 

 the shale between the Nautilus and 

 Strophalosia beds. 



P T E R I X O P E C T E N UNDOSUS. Hall . 



( Fig. 158.) (Pal. N. Y., Yol. Y., Pt. I., 

 ^Iv j^ p. 72. Pis. II.,LXXXII.) 

 ' ^- Distinguishing Cliaracters. — Length 



E'f ./) S' ureater than height; short hinge line; 



^ w ,....Iv.^*^#^' concave margins of ears and wing; 



"^,_C^-^ sharp, crenulated striae; concentric un- 



FiG. 158. ptermnpecten un- duhitious ; deep bvssal uotcli of right 



dosns. Small specimen, jn-e- ., i . 



serving both valves, and show- \ al\ C. 



ing strong undulations (^f rom ,^ i , .» \ • i i t-i • it/ \ 



Hall). l^ound ( . ) 111 the Deniissa bed (rare). 



Genus PTERINEA. Goldflss. 



[Ety. : Pteron, a wing.] 

 (1826: Peterfaot. Germ.) 



Yalves unecpial, left valve most convex. The shell is very 

 oblique, the wing large, and the ear small. Two or more 

 cardinal teeth and linear oblique lateral teeth occur. The 

 hinge line is straight, and has a linear flattened marginal 

 cartilage facet, which is longitudinally striat-i'd. The sur- 

 face of the shell is ornamented by rays. 



P T E KI X E A F L A B E L L A . 



(Conrad.) (Fig. 159.) (Pal. 

 \. Y., Yol. Y., Pt. L, p. 98, 

 Pis. XIY..XY., LXXXin.) 



Distinguisl] ing Cli ara cters . 

 — Large size; convex left 

 valve and flat or concave 

 right valve; large, well-de- 

 fined, triangular wing, with 

 concave margin; small, 

 rounded, well-defined ear; 



Fig. 159. Pterinea ftahelki. Left valve , i i i • , . 



(from Hall). sti-'oiig, rouiKted, (listaiit 



