96 UNIVERSITY OF COLORADO STUDIES 



feet, which have not yet been satisfactorily worked up. Dr. Sterki, who has examined our 

 material, suggests the importance of thoroughly studying the genus with reference to differ- 

 ences shown by specimens from various elevations. For this purpose large collections 

 from many localities are desirable, each lot from each locality to be carefully kept separate. 

 Dr. Sterki writes that "a forthcoming monograph of the North American Pisidia is 

 expected to give as much in the way of comparison of species with each other as can be given 

 in the present (or then) state of our knowledge," which will be an important contribution, 

 as the original descriptions were evidently not written for comparative purposes. 



[Concluded in next number of tliese "Studies."] 



EXPLANATION OF PLATES 

 Plate I 

 Fig. I. Anodonta grandis giganiea'Lea.. 



Fig. 2. Strophitus edentulus pavonius Lea. a, from Denver; b, from Greeley. 

 Fig. 3. Anodontoides ferussacianus Lea. 

 Fig. 4. Lampsilis ventricosa Barnes. 



Plate II 

 Fig. 5. Lampsilis anodontoides Lea. 

 Fig. 6. Lampsilis luteola Lam. 



Fig. 7. Unio tetralasmus camptodon Say. From Las Animas County. 

 Fig. 8. Sphcerium hendersoni Sterki. From Crow Creek, photographed from 

 cotypes, the first published figure. 



