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 tibise mostly orange—peculiarities 
which might elsewhere be varietal only. 
Norr.—Mr. Cockerell writes me that he now regards Phenacarion 
as a subgenus of Prophysaon.—Ed. 
‘ 
A FEW LAST WORDS ON CREPIDULA. 
BY JOHN FORD. 
In my article on Crepidula published in the 8th number of the 
Nauriius, I endeavored to show that the shells described by Say as 
C. glauca were altogether distinct from the C. fornicata of Linné, 
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- 
cata 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. fornicata 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. fornicata, 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. 
