. The elasmobranch fishes . Fig. 150. A heart of Heptanchus macuJatus. (Marie Weldt, orig.) B. Valves of conus, ven- tral view. (From Garman.) ap., aperture of last afferent artery; au., auricle (atrium) ; }''^, first and sixth bran- chial afferent arteries; , conus arteriosus; , left coronary artery; , hyoidean aft'erent artery; , pericardial; , ventral aorta; , valves of conus; vh., ventricle. which the blood enters from the sinus venosus (see p. 203, fig. 188, ), and from the latter of which it is expelled through the conus arteriosus {, fig. 150). The
. The elasmobranch fishes . Fig. 150. A heart of Heptanchus macuJatus. (Marie Weldt, orig.) B. Valves of conus, ven- tral view. (From Garman.) ap., aperture of last afferent artery; au., auricle (atrium) ; }''^, first and sixth bran- chial afferent arteries; , conus arteriosus; , left coronary artery; , hyoidean aft'erent artery; , pericardial; , ventral aorta; , valves of conus; vh., ventricle. which the blood enters from the sinus venosus (see p. 203, fig. 188, ), and from the latter of which it is expelled through the conus arteriosus {, fig. 150). The auricle, or atrium, is a greatly enlarged, thin-walled sac which lies dor- sall,y over the ventricle. Connecting it with the sinus venosus is the sinu- auricular opening. At the sides of this opening are the two sinu-auricular valves (sa., fig. 188), which prevent the backward flow of the blood into the sinus venosus upon the contraction of the auricle. Connecting the auricle with the ventricle is an auriculoventricular opening guarded by valves of the same name attached to the ventricular walls. The more or less triangular ventricle forces the blood by waj- of the conus arteriosus through the gill capillaries and as a consequence of the strain [160]
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