218 



the specimens are silicified, and I have been able thus to compare both 

 the interior and exterior with the originals, on which the species was 

 founded. 



2. 0. HiPPOLYTE, ante^ p. 81, occurs at Cow Head in Division P. 



Besides the above there are several small convex finely striated species 

 of the type of 0. perveta and 0. elegantula. The specimens are so badly 

 preserved that it would be useless to name them. They occui- at Port 

 aux Choix, Table-Head, Point Rich, and Bonne Bay. 



Stuophomena aurora. (N. sp.) 



Fig. 202. — Stropltomena aurora; a, ventral valve ; 6, section ; c, portion of the 

 surface enlarged. 



Description. — Semi-elliptical, length varying from a little more than 

 one-half the width, to four-fifths of the width, widest at the hinge line ; 

 contour usually an uniformly elliptical curve from the cardinal angles all 

 roimd. Ventral valve convex, narrowly and often acutely carinated on 

 the umbo, depressed and sub-concave towards the cardinal angles. Area 

 moderate, forming an obtuse angle of about 125^ with the plane of the 

 lateral margin. Dorsal valve concave, with a mesial sinus commencing at 

 the beak and grOwmg wider and shallower towards the front margin ; area 

 apparently about half the size of that of the ventral valve, and forming a 

 ri"'ht angle therewith. Surface with rather strong angular striiB of differ- 

 ent sizes, the smaller coming in between the larger, both by intercalation 

 and sub-division, the whole crossed hy fine concentric striae, more distinct 

 in specimens Avhich have the radiating striae well separated than in those 

 which have them close together. The striiB are about the size of those of 

 S. aUemata, but more angular. The concentric striae are just visible to 

 the naked eye when the surface is well preserved. On most specimens they 

 cannot be seen at all, as a vcr}'- small amount of Aveathering or exfoliation 

 removes them. In some there are several strong angular folds radiating 

 from the beak to the front margin, with usually one of the larger striae run- 

 ning along the crest of the fold, and a number of the smaller in the 

 intervening concave space. 



The convexity of this species, as indeed it is in all others of the genus, 



