PLATK XI— Continuefl. 



Genus DERBYA, Waagen. 



Page 261. 



Derbya Correana, Dcihy. 



Fig-. 18. Cardinal view of an internal cast of the pedicle-valve ; showing the (-avities left by the dental 



lamellae and meilian septum. 

 Fig. 19. The same specimen, viewed from above ; showing- the extent of the median septum. 

 Fig. 20. Cardinal view of an internal cast having a much higher area and a somewhat distorted beak. 

 Fig. 21. The exterior of a high cardinal area; showing the longitudinally grooved deltidium perforated 



near the lowei- part by a small oval foramen, which is probably accidental. From a gutta- 



per<'ha impression in a natural mould. 



Fig. 22. The interior of a jiedicle-valve ; showing the imion of the dental lamelli« with the median septum, 

 thus forming a subapical vault. 



Upper Carboniferous. Itaituba, Brazil. 



For the original illustrations of the two preceding species, see Bulletin of the Cornell Universitv. 

 Vol. I, No. 2. 



