686 JAMES L. KELLOGG 
ventral wall, and then posteriorly until they reach the end of the 
collecting membrane. Without extending itself, this membrane 
lies well within the base of the incurrent siphon, because of the 
Fig. 58 Barnea pacifica; g, position of gills; s, siphon. 
Fig. 59 Barnea pacifiea; em, collecting membrane; ig, inner demibranch of 
gill; m, portion of mantle thrown forward; og, outer demibranch of gill; pp, 
posterior palp; vms, visceral mass. 
Fig. 60 Barnea pacifica; ciliation of visceral mass; letters as in figure 59 
Fig. 61 Barnea pacifica; ventral view of visceral mass ciliation. 
Fig. 62 Barnea pacifica; ciliation of mantle edges seen from above; b, bay 
of mantle; fo, foot opening of mantle; me, fused mantle edges; v, vortex. 
