16 



Dorsal valve sub-quadrate, beak acute, sides rising abruptly to 

 the prominent mesial fold at an acute angle, giving it a triangu- 

 late aspect when viewed from the beak on a plane with the valve; 

 beak straight on a plane with the valve. Surface marked by 

 prominent plications, of which there are three on either side 

 of the mesial fold; these are crossed by concentric lamellae which 

 are well recurved, with projecting margins on the plications, and 

 are marked by fine, closely arranged, radiating striae. 



SPIRIFERA ASPERATA (N. Sp.). PI. 2, fig. 5. 



Shell gibbous, sub-rhombic ; cardinal extremities rounded, urn- 

 bones incurved, mesial fold wide, plications strong, hinge line 

 shorter than the width of the shell. 



Ventral valve prominently rostrate, area high ; placed on the 

 same plane with the valve ; foramen narrow ; beak curved well 

 over area. Dorsal valve sub-triangular in outline, beak abruptly 

 incurved and terminating at the hinge line. 



Surface with from four to five plications on either side of the 

 mesial folds, which is well defined. Radiating striae fine, thread- 

 like, sharply elevated, and are placed at nearly equal distances 

 apart, somewhat more than their diameter ; increase by interstri- 

 ation, and are asperate at regular intervals, the points being as 

 far apart as the distance between the striations. 



From the upper part of the shale. 



This species is distinguished from 6". eudora by the area of the 

 ventral valve being placed on a plane with the valve, and not 

 directed outwards, the narrow foramen and the beaks being more 

 strongly incurved. 



CRANIA DENT ATA (N. Sp.). PI. 2, fig. 6. 



Shell small, oval, apex pronounced, moderately acute, nearly 

 central, smooth; elevation to length as one to four; slope 

 slightly concave, with a small convexity near the posterior 

 margin. 



Surface smooth in the apical third; gradually becoming 

 ribbed towards the margin, where there are about thirty, which 



