184 IOWA STUDIES IN NATURAL HISTORY 
ingly interesting to make a similar investigation regarding the 
respiratory apparatus of this species, Ucides cordatus. The 
branchial chamber is tumid and the walls rather thin. It is 
lined by a membrane that is smooth to the touch and feels as if 
oiled. That portion which lines the dorsal part of the chamber 
is dark colored and seems covered with short tufts of villi. 
Holding it up to the ight it shows the impression of branching 
channels or sinuses resembling the markings on the inside of the 
human parietal bone. These sinuses appear to be between the 
membrane and the part of the carapace which it lines. The 
branchial chamber is partly divided into moieties by a shelf- 
like projection from the branchiostegite. All of the gills are be- 
low this shelf and are packed away horizontally in the lower 
part of the chamber, leaving the upper part quite empty. This 
arrangement differs from any other that I have seen. 
The wall bounding the branchial chamber on its inner side 
is rather delicate, membranous, and highly vascular. This is 
the body wall proper, dividing the branchial chamber from the 
real body cavity. Projecting from this wall, against which it is 
applied in an approximately horizontal position, is a strange 
structure entirely new to me. It is a tumid, bulging, somewhat 
S-shaped body, light in color and with rather thick walls. It is 
tubular in structure, but the tube diminishes greatly in diam- 
eter at each end, opens posteriorly into the body cavity and an- 
teriorly it seems to lead into a space in the suborbital plate just 
beneath the eyes, whence issues a large branching vessel applied 
to the lining of the upper part of the branchial chamber as 
already described. The lumen of the tube was filled with what 
appeared to be dried blood, although this interpretation may 
not be correct. Below the anterior concavity of the S-shaped 
body referred to, and attached to the branchial side of the body 
wall proper (which is here very thin and transparent) is a 
group of stiff slender projections which are tumid and usually 
clavate at their distal ends. They feel like cartilaginous strue- 
tures and project stiffly into the branchial chamber. There are 
six or seven of these curious projecting rods, some much longer 
than others. I have no idea as to their function, and find no 
reference to them in the literature at hand. One gets the idea 
