﻿BRITISH FOSSIL CEPHALOPODA. 



Plate I. 



Fig. 



1. Nautilus pompilius in its shell (after Valenciennes, reduced), a, the hood; 



b, the " tentacles " ; c, their sheaths ; d, the eye ; e, the front part of the 

 mantle ; /, the hinder part of the same ; g, the band of adhesion ; h, the 

 protrusion caused by the nidamental glands in the female ; i, vascular marks 

 in the mantle ; k, the septa ; I, their " necks " ; m, the siphuncle. 



2. The circulatory and respiratory organs (after Owen, but reversed and reduced). 



a, the great vein ; b, its perforations ; c, the common sinus ; d, the branchial 

 arteries ; e, their follicles ; /, two of the branchiae ; g, their stem ; h, the 

 branchial veins ; i, the systemic heart ; k, the siphonal artery ; I, the great 

 aorta. 



3. The mandibles (after Owen), a, the calcareous part of upper mandible ; b, 



the notched calcareous border of the lower mandible. 



4. The hood, seen from above (after Owen, reduced), a, the concave posterior 



border fitting to the convexity of the previous whorl ; b, the intervening 

 mantle fold ; c, the separated portion, or modified sheaths, surjporting 

 tentacles. 



5. General view of the anatomy of Nautilus pompilius (after Owen, reduced). 



a, the labial tentacles and their sheaths ; a', their folded band ; b, the upper 

 mandible ; c, the lower mandible ; d, the protractor muscles of the jaws ; e, the 

 retractors ; /, the hood ; g, the crop ; h, the gizzard ; i, the " pancreatic " 

 receptacle ; k, the intestine ; /, the liver ; on, the posterior aorta. 



6. View from behind to show the communications with the exterior (after Valen- 



ciennes, reduced), a, the overlapping lobe of the funnel ; b, the anus ; c, the 

 branchiae ; d, d', d", sacs over the pericardium ; e, their orifices ; /, section of 

 the nidamental gland. 



7. The cranial cartilage seen from below (after Valenciennes), a, the posterior 



side. 



