267 

 Genus ORTHONOTA. Conrad. 



[Ety. : Orthos, straight ; notos, back. ] 

 (1841 : Annual Report Geol. Surv. N. Y., p. 50.) 



Shells extremely elongate and inequilateral; anterior end 

 rounded, posterior truncate. Beaks near the anterior end. 

 Cardinal line straight, or sometimes slightly concave, extend- 

 ing nearly the entire length of the shell. Dmbonal slopes 

 rounded or angular, and denned by one or more distinct folds. 

 which extend to the post-basal extremity. Surface marked 

 by fine lines of growth, and often by strong undulations, 

 which are least conspicuous on the anterior end. Two or 

 more rounded or angular oblique folds extend from the 

 beaks to the posterior and post-basal margins. Cardinal 

 margin with a long linear fold embracing the ligament, which 

 is apparently internal. 



Okthonota (?) parvula. Hall. (Fig. 189.) (Pal. X. Y., 

 Vol. V., Pt. II., p. 482, Pis. LXV., LXXVIII.) 



Distinguishing Characters. — Elongate sub-trapezoidal 

 form ; straight ventral and dorsal 



margins; angular umbonal slope; - ■ •- - 



flat or slightly concave post-cardinal 

 slope ; fine surface stria?, and absence 

 of undulations. %kk*^ t **M |jl 



Found in the shale between the FlG . 189 . orthonota w par- 



vr j_-i i cu ii'ii • vula. Specimen retaining both 



JNailtllllS aild StrOphalOSia beds, 111 valves hi conjunction, x 2 (from 



Avery's Creek (one specimen). 



Genus CARDIOLA. Broderip. 



[Ety. : Kardia, the heart.] 

 (1884: Trans. Geol. Soc.) 



Shells with equal inequilateral valves, obliquely oval or 

 sub-circular; with large prominent obliquely incurved beaks. 

 Hinge line with a flattened cardinal area, which is widest 

 between the beaks, and extends for its whole length. Surface 

 radially plicated. 



