] 
70 ARTHUR WILLEY. 
posep a? ll mn 
Fie. 16.—N. pompilius, ¢. Dorso-posterior aspect of visceral region, to 
illustrate the circulus pallialis and the septal contour. x. m. Nuchal mem- 
brane. x.a. Nuchal artery. m.e. Free mantle-edge. p.z.a. Pallio- 
nuchal artery. m.p.a. Marginal pallial artery. co/. Columellar or shell 
muscle. p.c.a@. Posterior columellar artery. p. p. a. Posterior proventricu- 
lar artery. s.c. Septal contour. s. Siphuncle. p. s. a. Pallio-septal arteries. 
s.a. Siphuncular artery. 7. Liver. 7. Intestine. 7. Testis. post. p. a. 
Posterior pallial artery. g. Gizzard. 
N.B.—The dorsal aorta and its branches are indicated by dotted lines. 
They show dimly through the skin when injected. 
