137 



fig, 18. Fig. 19. 



From the data here given, it will be seen that the Genus 

 Cryptonella is nearly related to Centronella, though 

 both may perhaps be regarded by some palasontogists as of 

 only subgeneric value, differing as much from each other 

 as the former does from Renssel^eria, or as Terebratula 

 from Terebratulina or Waldheimia. Through this fortu- 

 nate discovery of Prof. Winchell, we are able in a perfect- 

 ly satisfactory manner to place these forms in their true 

 relations to other genera, which was before inferred from 

 the punctate structure, peculiarity of foramen, deltidial 

 plates and muscular impressions. 



It is not probable, however, that materials for other gene- 

 ra, or for reference to existing genera, are yet exhausted, 

 among the Terebratulidjs of the the Upper Silurian and 

 Devonian rocks. While engaged in these investigations? 



