SOME NEW DEVONIC FOSSILS 



241 



Rensselaeria callida nov. 



On other pages we have entered into some discussion of the 

 species of Rensselaeria of Trigerialike form occurring in Aroostook 

 county and at Dalhousie and have indicated their affinities with the 

 Coblentzian species R. strigiceps and R. crassicosta. 

 We have before us now extensive representations of two additional 

 species occurring in association which while presenting some aspects 

 of similarity to the species referred to (R. a 1 1 a n t i c a and 



Rensselaeria callida 



R. stewarti) are not in full agreement with them. One of these 

 here designated as R. callida occurs in various stages of growth 

 but the adult form is of considerable size, attaining a length of 

 50 mm and upward. Its valves are full, convex with a tendency 

 to gibbosity, the ventral valve being broadly and faintly keeled and 

 the dorsal valve slightly flattened medially, the ventral umbo ele- 

 vated and arching but not incurving over the other. The outline 

 is quite regularly oval. Beneath the beak the incurvature shows 

 no evidence of flattening into a cardinal area as in the species cited 

 nor is there evidence of such area on the dorsal yalve. There are 

 a well defined foraminal opening and tube and the dental plates 

 are considerably developed extending from one fourth to one 



