Miocene Barnacles from Gay Head. — Citslunan. 295 
American I'.alamis ni the Miocene. His specimens were from 
\'irsinia and ATaryland, while Conrad's type of D. prof ens was 
also from \iroinia. Darwin iinds that the opercular valves 
agree in their details with those of H. concavns T.ronn which 
was described m 1831, several years before the first appear- 
ance of the description of B. protens Conrad. The very small 
use that can be made of the exterior shell is sliown by the 
comparisons made by the two writers. Conrad speaks of his 
species as being close to the English B. crassns. A comparison 
of the opercular valves of his species with B. crassus would 
have shown a4; once the great dissimilarity of the two, although 
in many ways similar in external form. In the outer shell 
also one has the radii perforate, the other imperforate. 
In his remarks toward the end of his monograph of the 
Cirripedia, Darwin speaks of B. protens as follows, '"I cannot 
recognize this species; it resembles /?. /'o;r(r/;/,s-; but as the radii 
are rather narrow, and apparently with rather oblique sum- 
mits, it may be B. coiicaz'ns; the opercular valves are not fig- 
ured." Here again, the likeness to B. porcatns would at once 
have been seen to be entirely superficial if the opercular valves 
of the two could have been compared. 
A considerable number of s]>ecimens from Mrginia and 
Maryland, labelled B. protens and corresponding in all points 
with Conrad's figures have been examined by the writer. With- 
out exception the opercular valves were like those of B. 
concavns as figured by Darwin. Xot only this, but in the 
series obtained, the very slight diflferences noted by Darwin 
were bridged over by the specimens, many of them being 
more like the figures of specimens from the English Crag 
than those figured from .^Maryland. Darwin, however, notes 
the variability of the ^Maryland specimens. 
The specimens obtained at Gay Head are like B. concavns 
in having the basis and parieties i)ermeated by pores. The 
opercular valves where shown were similar to those of B. 
concavns. Fig i, especially to those of young specimens. It 
should undoubtedly be recorded as this species. Its occur- 
rence on the backs of crabs is also in favor of its being placed 
under that species, which in its recent members is almost al- 
wa\s found attacJied either to tlie backs of crabs or to sholls. 
