128 THE NAUTILUS. 



Phenacarion might almost be a variety of Prophysaon hemphilli, 

 except for the generic character. Possibly Prof E. D. Cope would 

 regard this as an instance of "the same specific form" existing 

 "though a succession of genera," which he has regarded as probable 

 in his " Origin of the Fittest" (quoted by Wallace, " Darwinism," p. 

 421). Indeed, it not very rarely happens that almost the only 

 difference between two species is a generic one. Good instances of 

 this are afforded among the Hymenoptera, e. g., the resemblance of 

 Vipio coloradensis Ashm., to Agathis vulgaris Cress., is almost exact 

 on superficial examination. Except the generic and family char- 

 acters, the Agathis is only a little larger with entirely fuscous wings, 

 and the posterior femora and tibi?e mostly orange — peculiarities 

 which might elsewhere be varietal only. 



Note. — Mr. Cockerell writes me that he now regards Phenacarion 

 as a subgenus of Prophysaon. — Ed. 



A FEW LAST WOKDS ON CREPIDTILA. 



BY JOHN FORD. 



In my article on Crepidula published in the 8th number of the 

 Nautilus, I endeavored to show that the shells described by Say as 

 C. glauca were altogether distinct from the C. fornieata of Linne, 

 and therefore the name should have been retained in Bulletin No. 30 

 of the National Museum recently published by Dr. Dall, instead of 

 discarded. As in the following number their distinctness from forni- 

 eata was acknowledged by Dr. Dall, no further evidence seems 

 necessary to sustain it. 



The assertion by him however in the same issue, that the series of 

 shells presented by me to the National Museum under the name of 

 C. glauca " are distinct from C. fornieata but that they do not show 

 the characters called for by Say's description, " does, perhaps, 

 challenge further remark ; since it appears to be partly correct and 

 partly conjectural. They are certainly not C. fornieata, but they as cer- 

 tainly do embody every character called for by Say's description of the 

 true C. glauca written in 1821-2, and published in Vol. 2, Journal 

 of the Academy of Natural Sciences of Philadelphia ; also in Say's 

 Conchology of the United States. 



