760 



ZOOLOGY 



SECT. 



less completely united in the middle so as to form a transverse 

 ridge ; these are the aboral osphradia (p. os.). In the middle line 

 of the mantle-cavity is the anus (an.), a large aperture with minutely 

 lobed margin, situated on a slight elevation, but by no means so 

 prominent as in Sepia. On each side are two apertures, the oral 



r. ant.cs 



I. neph. 



an. 



p. OS 



pl.neph 

 L.visc.ap 



FIG. 689. Nautilus pompilius, interior of mantle-cavity of a male specimen with the 

 postero-ventral wall reflected, a. I, neph. oral left renal aperture ; an. anus ; cten. ctenidia ; 

 en. eye ; /. funnel ; 1. $ ap. left reproductive aperture indicated by a bristle passed through 

 it ; I. vise. ap. left viscero-pericardial aperture ; n. s. Needham's sac ; pen. penis ; pt. neph. 

 aboral left renal aperture ; p. os. aboral osphradia. ; r. ant. os. right oral osphradium ; v. n. 

 visceral nerves. (After Willey.) 



and aboral renal apertures (Fig. 689, a. I. neph., pt. neph.), corre- 

 sponding to the single pair of Sepia, but not elevated on papillae. 

 Close to each posterior renal aperture is an opening the viscero- 

 pericardial (1. vise, ap., r. vise, ap.) leading into the pericardial 

 section of the cceloine ; these are not represented in Sepia. In 

 both sexes there are two reproductive ducts, right and left ; but 



