820 DESCBIPTION OF PLATES. 



Figg. 3 and 4. Diagrammatic sections through the cephalopodium of female (3) and 

 male (4) to elucidate the tentacular formula suggested in the text. The ophthalmic tentacles 

 are not included in the diagrams. On the left of fig. 4 there is the scheme of enumez'ation 

 of the digital tentacles of the outer whorl, the tentacles being here regarded as marginal 

 appendages of a sinuous pleural fold or epipodium. 



c.p. Marginal papillae of the mouth. 



m.i. Inferior mandible. 



s.s. Superior symphysis of the cephalopodium. 



i.s. Inferior symphysis. 



/ Funnel. 



ext.t. Outer whorl of the cephalopodium. 



int.t. + inf.o. Inner whorl. 



inf.o. Infrabuccal organ. 



Fig. 5. N. pompilius <$ . Dissection from below to illustrate, among other points, the 

 ventral symphysis of the cephalopodium which presents a deep concavity, f.i. the fossa 

 infundibularis, to receive the funnel. The numbers are placed upon the sheaths of the 

 tentacles involved in this view, in accordance with the scheme of enumeration here adopted. 

 The funnel has been sliced away to its roots and the vena cava and endochondral sinus 

 laid open to expose the fenestrations in their dorsal wall. 



r.i. Radix infundibuli. 



c.i. Cartilage. 



a.i. Ala infundibuli. 



v.i. Vena cava. 



s.m. Shell-muscle (cut across). 



n.s. Needhamian vesicle. 



e. Eye. 



Fig. 6. N. pompilius. Dissection of the cephalic sensory complex from the right side, 

 showing also the origin in sequence from the coronal (pleuro-pedal) ganglion, of the nerves 

 of the sixth, seventh and eighth digital tentacles. 



a. Infundibular artery traversing the cartilage. 



a.i. Cut surface of ala infundibidi. 



c. Cartilage. 



c.v. Cerebro-visceral nerve-centre. 



h. Cut surface of hood. 



/. Limbus infundibidi. 



a. Olfactory labyrinth (rhinophore) laid open. 



•n.m. Nuchal membrane. 



n.n. Olfactory nerve. 



o.p. Posterior ophthalmic tentacle. 



op.n. Optic nerves. 



of. Otocyst, lying over against the coronal ganglion, concealing the mass of the latter 

 (cf. PL LXXXII. fig. 6). 



s.m. Surface of shell-muscle. 



v. Infundibular vein. 



Fig. 7. N. pompilius. Dissection of the nuchal complex from above. The hood and 

 nuchal membrane have been divided along the mid-dorsal line and the halves drawn apart, 



