318 MYA. 



within, varied with green ; no cavity under the 

 beak. Dimensions two and a half inches by 

 one and two thirds. 



ovata, shell but middling, suhovate, convex, not 

 remarkably thick, horn-colour, not radiated, 

 flattened and fuscous on the anterior margin : 

 beaks decorticated and placed nearer central ; 

 boss prominent ; pearly within ; cavity of the 

 beak capacious ; primary teeth very oblique, 

 almost parallel to the posterior margin and 

 much compressed. Dimensions four inches by 

 three. 



cariosa, shell but middling thick, long forward, 

 short back of the beaks ; olive-green, sometimes 

 radiated with green and with interrupted wrink- 

 les in longitudinal rous ; beaks somewhat pro- 

 mine.nt, distant, carious, wax-yellow beneath the 

 epidermis ; concavity bluish-white ; teeth often 

 subconic and crenate. Dimensions two inches 

 and a quarter by one and a half. 



ochrocea, shell thin, fragile, translucent, suhovate : 

 hinge margin straitish ; pale-olive or orange ; 

 often with green wrinkled radii ; anterior mar- 

 gin wrinkled ; beaks decorticated and near, 

 with two or three concentric undulations ; bluish- 

 white or yellowish within, reddish near the 

 base ; teeth very oblique and much compressed. 

 Dimensions an inch and a quarter by an inch 

 and three quarters. 



nasuta, shell thin, oblong, compressed, beaked, 

 horn-colour or fuscous, wrinkled, with green 

 radiations ; bluish-white within ; teeth crenate ; 

 scarcely any back-cavity. Dimensions about 

 one inch by two and a half. 



