REPORT OF THE DIRECTOR, 1922 99 
All the specimens of Eobalanus informans are so com- 
pletely flattened that we get a flat projection of the wall only, and 
we do not know how high the latter was or how the shell looked in 
the profile view. From the fairly wide interspaces between the com- 
partments, even after they have been flattened down; and from the 
lack of overlapping among them, it appears that there existed very 
wide interspaces occupied by connecting chitinous bands when the 
plates were raised to any fairly steep angle. It is therefore probable 
that the wall was not at all rigid as in the recent Balanidae, where 
only the plates bounding the cavity for the mouth and feet (scuta 
and terga) are movable; and that the animals of Eobalanus were 
still enjoying a certain freedom of movement and correspondingly 
less protection, which may explain their scarcity among the Ordo- 
vician fossils. | 
Scuta and terga which form the valvular carapace or operculum 
of the upper aperture of the later Balanidae and the Lepadidae and 
which are of great systematic importance, have not been found in 
Kobalanus and Protobalanus, and in our view did not yet exist, but 
are a later development designed to close in more completely the 
_ ventral side. They are not fundamental structures. The compart- 
ments still being movable along their basal hinge, the creatures could 
probably close the ventral side by drawing the compartments suffi- 
ciently far inward. 
It is a fact worth noting in this place, that all four specimens of 
Eobalanus, thus far observed, were found on the upper side of the 
living chamber of cephalopods, three of them rather far forward. 
We take this to mean, that just as certain recent barnacles are local- 
ized on the head of the cachelot whales, where they come in contact 
with the most water and most easily procure food particles, so also 
the species of Eobalanus may have found it advantageous to attach 
themselves where they would secure the most food and at the same 
time be least liable to be covered with mud, when the cephalopod 
dragged its shell over the bottom of the sea. 
