236 



and prominent; foramen limited below by well-developed del- 

 lidijil plates. Brachidium consisting of ;i loop bent back 

 upon itself, the juncture of the branches occurring a little 

 below the plane of their origin. 



Cryptonella planirostris. Hall. ( Fig. 147.) (Pal. 

 X. V.. Vol. IV.. v . 395, PI. LXI.) 



Distinguishing Characters— Great convexity of valves; 

 large size of adult ; often truncate front and consequent sub- 



w W 



Fig. m: Cryptonella planirostris. Dorsal, ventral, and profile views of a large, strongly- 

 marked individual ; enlargement of beak of pedicle valve ; dorsal, ventral, and profile views 

 of a smaller and less strongly-marked individual (from Hall I. 



pentagonal outline of valves; angular umbonal margins of 

 pedicle valve, with Hat or concave faces on either side of the 

 deltidial plates. 



Found in the Encrinal limestone, at Section 5 (common i. 

 Doubtful specimens have been found in the shale between the 

 Encrinal and Pleurodictvum beds. 



Cryptonella rectirostris. Hall. (Fig. 148.) (Pal. 

 X. V.. Vol. IV.. p. :; ( .)4. PI. LXI.) 



Distinguishing Characters. — Usuallv small size: sub-rhom- 



boidal outline: frequently trun- 

 cated front: erect beak, with 

 inflected cardinal margins. 

 Found in the Pleurodictvum 



Fia.148. Cryptonella rectirostris. Dor- beds, ill Avery's Creek, and Oil 

 sal, ventral, ana profile views of a speci- , T 1 .,1 



men (from Hail). the Lake Shore (common). 



a 



