PARKER AND DAVIS : HEART BLOOD VESSELS IN FISHES. 173 
mann (’09, p. 9, Tab. 1, fig. 2), who also figured the openings of 
six small vessels belonging to the cardjac veins. 
In Amia calva the superficial veins of the heart (PI. 3, fig. 9) 
open into the venous sinus by a single orifice which lies posterior 
and slightly to the right of the sinu-auricular aperture ( ap .). 
Prom this opening two veins, the right (vn. cor. dx.) and the left 
(vn. cor. s .) coronary veins, encircle the heart at the level of 
the coronary sulcus and anastomose so freely on the ventral side 
(Fig. 12) that a ring vessel is established. From the right coro¬ 
nary vein (Fig. 9, vn. cor. dx.) two branches are given off, one 
anteriorly to the right side of the cone, and the other posteriorly 
to the same side of the ventricle. From the left coronary vein 
(vn. cor. s .) a corresponding pair of branches is given off; that 
to the cone, however, is small and more ventral (Fig. 12) in posi¬ 
tion than its fellow of the opposite side. From the ventral anas¬ 
tomosis of the coronary veins a single vein extends over the 
median ventral surface of the ventricle (Fig. 12). This probably 
represents a branch from the left coronary vein. The coronary 
veins of higher fishes have generally escaped attention. Pose 
(’90, p. 35) mentions them as present in Pimelodus catus and 
Tetrodon 2 ^hysa, but absent from the eel; and Martin (’94, p. 21) 
states that in the salmon the right coronary vein only is present 
and this opens into the auricle. That there is a unilateral condition 
of the coronary veins as well as of the arteries in the higher fishes 
is not imj3ossible. 
Vessels of Thebesius. 
The vessels of Thebesius seem heretofore never to have been 
sought for in the hearts of fishes. We have endeavored to ascertain 
whether they were present in the three species which we have 
studied. 
On inflating the left coronary vein of a fresh heart of Car- 
charias littoralis by means of a blowpipe, the auricle was gradually 
distended with air. As the entrance of air into the auricle through 
the sinu-auricular opening was carefully guarded against, such air 
as found its way into the heart must have come through some 
other aperture. If a heart whose auricle is distended with water be 
inflated as described above, bubbles will be seen forming on the 
inside of the left wall, and if the opposite wall be removed, these 
