PLATE VI. 
fleart of Ophiodon elongatus. 
Fic. 39 is from a photograph of the posterior half of a large Ophtodon’s heart, 
looking inward and caudad. ‘This heart had previously been injected 
with a gelatin mass and hardened in formalin, and the cut was made 
directly between the anterior and posterior auriculo-ventricular valves. 
x4: 
40. As above, is a photograph of the ventral side of a large Ophzodon’s 
heart. A portion of the ventral wall of the ventricle had been removed 
to the depth of the central cavity to show the semi-lunar and auriculo- 
ventricular valves. X 2. 
Abbreviations used. — Aur., Auricle. A.V.O., Auriculo-ventricular opening. 
A.V.V., Auriculo-ventricular valves. B.Art., Bulbus arteriosus. C.Art., Conus 
arteriosus. C.C.V., Central cavity of the ventricle. C.T., Connective tissue. 
L.F., Longitudinal folds or ridges. M.L., Muscular layer. S.A.O., Sinu-auric- 
ularopening. S.A.V., Sinu-auricular valves. S.V.,Semi-lunar valves. S.Ven., 
Sinus venosus. T.C.A., Trabecule carne auricle. T.C.V., Trabecule carne 
ventricle. V.Ao., Ventral aorta. Ven., Ventricle. 
Text-fig. 1. — Represents a transverse section through the auricle and ven- 
tricle of Ophkiodon elongatus. This section was made through one of the auric- 
ulo-ventricular valves. Camera lucida. Leitz No. 2 obj. with lower lens 
removed. 
Text-fig. 2. — Camera drawing of transverse section through the region of 
the conus arteriosus. Same obj. as above. 
Abbreviations used. — Aur., Auricle. A.V.Y., Auriculo-ventricular valve. 
C.T., Connective tissue. E.M.F., Elastic muscle fibers. End., Endothelium. 
L.M., Longitudinal muscle fibers. S.V., Semi-lunar valves. T.M., Transverse 
muscle fibers. Ven., Ventricle. 
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