OF DENISON UNIVERSITY. 79 



beaks rather prominent, incurved, situated over ]^ from the front 

 margin; ventral margin rather evenly curved; posterior margin ellip- 

 tical ; anterior margin curved abruptly below, but passing by a nearly 

 straight line to meet the produced hinge at nearly right angles. The 

 escutcheon is well defined by a strong post-umbonal ridge ; lunule 

 well-marked. Greatest convexity near the middle ; surface covered 

 with fine, close lines of growth. Length lo mm; height 7 mm, 

 thickness 4.5 mm. The state of preservation forbids positive identi- 

 fication. 



Muculana iLeda) spatulata, ^p. n. 

 (Plate IX, Fig. 11, (12?) Plate VII, Figs. 35.) 



Shell elongate oval, broadly expanded anteriorly, acute behind; 

 beaks small, slightly prominent, acute, about seven-twentieths the en- 

 tire length from the anterior margin ; hinge-line rather strongly con- 

 cave ; teeth (if present) small ; anterior margin forming a bold, uni- 

 form curve, reaching nearly as high as the beaks, with its greatest an- 

 terior projection above or near the middle; lower outline gently con- 

 vex, nearlv attaining the hinge posteriorly, but separated from it by a 

 short truncate posterior margin. Greatest convexity about one-third 

 the height of shell from the beaks; umbonal ridge with a sudden, but 

 gentle slope. The surface is marked by very numerous, fine lines of 

 growth — about six occupying the space of i mm, in the shells meas- 

 ured. Length [i] 20, [3] 17, [3] 16.5; height [i] 9, [2] 7, [3] 8; dis- 

 tance from beak to front [i] 4, [2] 3, [3] 3; height of beak above 

 longest transverse axis ]i] 7, ]2'| 6, [3] 5. From Leda bellistriata of 

 the coal measures, which it greatly resembles, it differs in being more 

 expanded anteriorly, and having the most convex part of the anterior 

 margin higher than the middle. Shales below congl. L It is possible 

 that this is Dr. Stevens' species, if so, however, its identification in the 

 coal-measures must be regarded as erroneous. 



^ucidana {Leda) s'nniUs, sp- "• 

 (Plate IV, Fig. 15.) 

 Shell large size, elongate, twice as long as high, rather flat ; beak. 



