TOPOGRAPHICAL EELATIONS AMONG THE DOCOGLOSSA. 289 



Plate 16. 



Fig. 11. The gut of Acmcea virginea, A. testudinalls, or A. corticata. 

 Figs. 13 & 13. The proximal and distal portions of the gut iu Patella vulgata. 

 Figs. 14 & 15. The proximal and distal portions of the gut iu Patella ccerulea. 

 Fig. 16 a. The heart and pericardium of the hypothetical Prostreptoneure. 



16 6 & c. Hypothetical diagrams illustrating the transition to the condition in the primitive 



Docoglossa. 



17 a. The heart oi Lottia viridula. After Haller. 



17 6. The heart of Patella vulgata. 



18 a. Oblique section through the pericardium of Acmaa. 



Plate 17. 



Fig. 18 6. Oblique section through the pericardium oi Patella. 



19. Dorsal view of Acmcea testudinalis after the removal of the shell, the pigmented epithelium, and 



the roof of the branchial cavity. 



20. Corresponding view of Patella vulgata. 



21 a, b, k, c. A portion of the manile-edge in Acmeea testudinalis, A. virginea, and P. vulgata 



respectively. 



22 a-f. A series of transverse sections through region A of the gut of Patella vulgata, showing 



merely the longitudinal folds. 



23. A corresponding diagram, showing the maximum torsion observed in Acmcea virginea. 



24. A transverse section showing the renal communications of the reno-pericardial canals iu 



Patella. 



Meference Letters used in the Flates. 



A. = Fore-gut or special secretory region. 

 An. = Anus. 



Ant.Ao. = Anterior aorta. 



Ao. = Intrapericardial " Bulbus Aortae " in fig. 18. 



B. = Wide region of absorption and admixture of secretions in gut. 

 B.Gl. = Buccal glands. 



Br.C. = Branchial cavity. 



C. = Intestinal region of gut. 

 Ct. = Ctenidium. 



D. = Terminal region of intestine. 



D.F.G. = Folds which are dorsal in the gullet-wall. 



E. = Eye. 



EP. = Epipodium. 



F. = Foot. 



Gl.M. = Glands of mantle-edge. 

 G.M.T. — Greater mantle- tentacle. 

 G.M.V. = Great mantle-vein. 

 H.P. = Great digestive gland. 

 K.B. — Boundary between the two kidneys in fig. 24. 



L. = Si)ccial wide loop of intestine (region C) which immediately follows region B in Acmaa, 

 Patella, &c. 

 L.Au. = Left auricle. 

 L.Ct.V. = Left cfl'erent etenidial vein. 

 L.K. = Left kidney. 

 SECOND SERIES. — ZOOLOGY, VOL. IX. 41 



