A. E. Verrill — North American Cephalopoda. 337 
is divided into two chambers by a median, thin, membranous par- 
tition. 
The branchial chamber is separated from the visceral cavity by a 
thin, translucent membrane, through which there are two circular 
openings («), one a short distance in advance of the base of each gill ; 
through these the secretions of the urinary organs (r, r) are doubtless 
discharged. Internally the visceral cavity is divided into several com- 
partments by folds of thin membrane. The largest of these chambers 
contains the stomach and its ccecal lobe (S, S'). When the branchial 
cavity is opened on the ventral side, as in PI. XL, fig. 1, and the 
thin membranes covering the viscera are removed, the renal organs 
(r, r') are seen, as large and conspicuous organs, especially if the 
venous system has been injected with a colored fluid. These organs 
are situated below, above, and in front of the heart, but two pyri- 
form glands (/•', r'), which are firmer and have a more compact struc- 
ture than the rest, extend along the posterior venae-cavae. The an- 
terior ones, in front of the heart, consist of a number of groups or clus- 
ters of lobulated glandular follicles, developed upon the posterior 
part of the anterior vena-cava and upon its saccular divisions, on the 
hepatic veins, on the intestinal veins, and on other large veins going 
toward the branchial auricles ( au ). Two of the larger divisions (r, r), 
which are elongated, and lie below and across the heart and large 
efferent vessels (bo) returning from the gills, arise as direct forks of 
the vena-cava, which divides just in front of the origin of the intestine ; 
these forks pass each side of the intestine and each gives off a dorsal 
branch, which runs up along the basal part of the intestine and joins 
the large saccular renal vessels that lie above the heart, on each side. 
These dorsal, renal vessels extend backward beyond the heart; they 
receive the blood from the gastric veins posteriorly and from two 
hepatic veins anteriorly ; laterally, they communicate directly with 
the branchial auricles. 
The ventricular heart (IT) is a rather large, muscular, median, some- 
what unsymmetrical organ, varying in shape according to the state 
of contraction. Usually it is more or less obliquely four-cornered, 
with the right side largest and the posterior end more or less conical. 
From the posterior end arises a large artery, the posterior aorta, 
which gives off, close to its origin, two small arteries ; one of these 
is median, and goes forward to the ink-sac, passing below the heart ; 
two branches, close to its origin, go to the renal organs (r, /•), on each 
side; the other, arising laterally, goes to the prostate gland and other 
organs connected with it, (PI. XL, fig. 2, po). A little farther back 
