826 DESCRIPTION OF PLATES, 



black retina except over the inner surface of the opaque cornea which appears as a black 

 disc perforated by the pinhole orifice. 



The dorsal border of the eye is smooth and convex, the ventral border limbate. x 3. 



r. Rhinophore. 



Fig. 26. View of the anterior portion of the peri-oesophageal haemocoel. The body has 

 been divided in the nuchal region. The visceral nerves are seen radiating out from the 

 visceral ganglionic commissure. 



d. Diaphragm (the darkly shaded area in front of and above the bifurcating aorta) 

 separating the peristomial haemocoel from the peri-oesophageal haemocoel. 



a. Aorta. 



n.in. Nuchal membrane. 



h. Hood. 



oe. Oesophagus. 



8.m. Shell-muscle. 



v.c. Vena cava. 



f.o. Funnel-organ. 



a.i. Ala infancUbuli. 



Fig. 27. The funnel with the flaps pressed open to expose its internal surface. The 

 regions of the crura and alae are separated by the anterior borders of the cartilage appearing 

 as oblique, wliitish bauds. Between the crura occurs the tongue-shaped valve, the free border 

 of whicli is approximately concentric with the anterior border of the funnel. 



f.o. Funnel-organ. 



Fig. 28. Dissection of an injected specimen to exhibit the recurrent course of the 

 tentacular artery. (Cf. also PI. LXXXII., fig. 5.) 



a. Aorta. 



r.m. Roots of dorsal retractor muscles. 



c.e. Cerebral ganglionic commissure cut across ; the root.s of the two stomatogastric 

 nerves of the right side are seen beyond the cut edge, but the demarcation of the cerebral 

 commissure could not be well indicated in this drawing. 



g. Coronal (pleuro-pedal) ganglion. 



r.a. Recurrent tentacular artery. 



Fig. 29. Dissection of the buccal cone from the right side, to illustrate the topography 

 of the stomatogastric system. 



r.m. Retractor muscle. 



«. Buccal artery. 



r. Radular caecum. 



n'. and n". Stomatogastric nerves meeting in the pharyngeal ganglion below the border 

 of the wing-like expansion of the lower mandible {ir. is cut across shortly before the union). 



h.c.^ and b.cr Buccal commissures proceeding from the pharyngeal ganglion. 



