DESCRIPTION OF PLATES. 819 



genital or, as called in the text, the genito-intestinal ligament, which represents a median 

 mesentery, x 3. 



t. Testis, derived from and adherent to the right side of the mesentery , on the opposite 

 side is the gastric ligament passing across to be inserted into the wall of the stomach (st.). 



p.a. Posterior pallial artery, seen traversing the middle pallio-visceral fontanelle (cf. 

 PL LXXXII. fig. 7). 



si. Siphuncle. 



Figg. 21 and 22. Details of preceding, to elucidate the relations of the transverse and 

 longitudinal loops of the intestine. Fig. 21 shows a portion of the intestine and right liver 

 in normal juxtaposition. In fig. 22, the liver has been cut away so as to expose the 

 intestine and the longitudinal loop of the latter has been turned forwards. 



t.i. Transverse loop of the intestine. 



d.i. and a.i. Descending and ascending limbs of the intestine. 



oe. Narrow portion of the oesophagus proceeding from the fundus of the crop to the 

 stomach (st.). 



py. Pyloric caecum with bile-duct opening into its apex. 



b.d. Bile-duct, above or behind which the intestine passes. 



Fig. 23. Pallio-visceral region of another specimen older than that of fig. 20, but showing 

 the same primary relations of the mesentery. 



y. Pyriform gland. 



st. Stomach traversed in this specimen by constrictions. 



p.a. Posterior pallial artery. 



d.i. and a.i. Intestine. 



r.l. Right liver. 



PLATE LXXXI. 



Fig. 1. N. pompilius. Dissection of a relaxed specimen from the right side, showing 

 the relation of the capito-pedal cartilage to the siphonopodium and to the cephalopodium. 

 The alae infundibuli have been cut away. 



/. Funnel (crura infundibuli). 



I. Limbus. 



c. Cartilage. 



v. Infundibular vein. 



a. Infundibular artery. 



r. Rhinophore. 



o.a. and o.p. Anterior and posterior ophthalmic tentacles. 



e. Eye. 



1 — 11. sheaths of digital tentacles; that of the second tentacle (2) comprises an anterior 

 portion forming part of the hood and a posterior portion ; the third sheath (3) is wedged 

 in between 2 and 4, only its anterior end being visible in this view. 



Fig. 2. Diagram of Nautilus to illustrate the theory of orientation. The dotted line 

 denotes the presumptive antero-posterior axis. 



I. Limbus. 



a.i. Ala infundibuli. 



s.m. Shell-muscle. 



m. Mantle. 



s.ffl. Septal aponeurosis. 



w. vi. 107 



