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SIPHUNCLE AND PALLIAL VESSELS. 



into two main submarginal arteries (m. a.) from which numerous radial arteries (r. a.) 

 proceed to the mantle-edge. 



Fig. 3. N. pompilius, ? . View of ventral surface of pallial and visceral regions, to show the course of the 

 pallial arteries; /. funnel; m.e. free edge of mantle; r.n, radial pallial arteries; m.a. marginal pallial 

 artery; a.p.a. anterior pallial artery; n.g. region of nidamental gland; b.o.a. branchio-osphradial artery; 

 s.m. shell-muscle ; r.o. region of renal organs ; h. heart ; p.p.a. posterior pallial artery ; g. gonad ; 

 i.a. intestinal branch of anterior pallial artery. [From Quart. J. Micr. Sc. Vol. 39, 1896.] 



Exactly at the point where the anterior pallial artery passes into the substance of 

 the mantle, that is to say at the level of the anterior limit of the renal region, a pair 

 of lateral branches arise almost at right angles to the main vessel. I suggested the name 

 branchio-osphradial for these arteries (b.o.a.) since among their minor ramifications they 

 send branches up to the tips of the branchiae supplying the integument of the latter, 

 and also a small branch into each of the four osphradia. In the female they also 

 supply the nidamental gland. The branchial branches of these arteries are of the nature 

 of arterioles or intrinsic arteries of the gills in their capacity of fleshy organs. 



