The anatomy of Lucapina crenulata. 



465 



the point where the posterior and anterior canals join, the palliai 

 sinus bends in and back, running parallel and somewhat connected 

 with the efferent branchial sinus. Near the outer base of each ctenidium 

 the blood from the palliai sinus joins that from the gill and enters 

 the auricle. 



Fig. M. Mantle circulation with relation to ctenidia and heart (dorsal view). 

 A anus, Af afferent branchial sinus, Ate auricle, Bas basibranchial sinus, Ct ctenidium, 

 Ef efferent branchial sinus, 31 edge of mantle, 31. c mantle cavity, P. c pericardial 

 cavity, P. s jjallial sinus, R rectum, E.P reno-pericardial duct, v ventricle. 



The wall between the efferent branchial sinus and the palliai sinus, 

 is composed of a network of muscular fibers, so that the blood from 

 the two sources intermingles more or less freely before its final com- 

 bination at the bases of the ctenidia. 



