294 
The American Geologist. ^'ovember, i904. 
the matrix. In all, a number of specimens of crabs with at- 
tached barnacles were found, one crab with several, more or 
less crowded tog^ether. Fi^ 2. All the specimens were of 
young individuals. Figures of these are given. 
Figs. 1-3. Balamis concavus froiT. the JNIiocene of Gay Head. Fig. 
I. Enlarged view of basis and one opercular valve. Fhe outer shell ha.s 
been entirely lost. Fig. 2. Part of a group of young specimens upon a 
crab's back. Here again the shell itself has been dissolved away. Fig. 3. 
Cast of interior showing shape and the tendency toward plications. 
(Specimens in Museum of Boston Society of Natural History-.) 
Fragments of a Balanus were reported from Gay Head 
by Dr. W. H. Dall.(Am. Journ. Sc, 3rd series, vol. xlviii, p. 
297) as "Balanus ( Pproteus Conr.) fragm."' Almost without 
exception our JNIiocene barnacles from the eastern United 
States have been referred to Balanus pro feus Conrad. The op- 
ercular valves were not figured by Conrad, two sketches of the 
external view of the whole shell l^eing all that is given in his 
Medial Tertiary. The original description was not accom- 
panied by a figure. 
Darwin was the first to recognize the real nnportance of / 
the inner or opercular valves as a means for separating the 
species of Balanus. He showed that while the outer shell or 
testa varied with the irregularity of the surface to which it 
was attached, the inner opercular valves were not so attectcd. 
Darwin, in his monograph of the Fossil Balanida; (1854.) 
figured for the first time the opercular valves of the common 
