ox THE MORPHOLOGY OF THE CEPHALOUS MOLLUSCA I93 



Fig. 6. Nervous system, with the termination of the pedal artery at/. 

 Fig. 7. Cerebral ganglia from below. 

 Fig. 8. Right eye and tentacle. 



Pi., in. [Plate iS] Atlanta Lesuerii. 



Fig. I. Animal in its shell (much magnified), from the right side. Male. 



Fig. 2. The same from the left side, to show the arrangement of the nervous and \ascular 



systems. 

 Kg- 3- Post-abdomen, without the shell ; more enlarged, from the right side. 

 Fig. 4. Portion of the mantle-cavity and post-abdomen from the left side, to show the 



arrangement of the heart and branchije. 

 Fig. 5. Portion of the penis. 

 Fig. 6. Cerebral ganglia, from the left side. 



PL. I\". [Plate 19] 



Fig. I. Pneuiiwdeniwn ? A young specimen, to show the form of the foot and its 



relations. 

 Fig. 2. Euribia Gaudichatidii (Eydoux and Souleyet), from behind, placed, not as it 



swims, but so as to leave its parts in their normal position. This has been 



done with each of the figures in this Plate, except it be otherwise expressly 



mentioned. 

 Fig. 3. The head and foot of Euribia, seen from below. 

 Fig. 4. Cleodora ciirvaia (Eydoux and Souleyet), from the neural side. 

 Fig- 5. The same, from the hremal side. 



Fig. 6. Cleodora aciciilata, from the right side, without the shell. 

 Fig. 7. The same. The head and aU"E from the neural side. 



PL. \'. [Plate 20] 



The first eleven figures are to be regarded as mere diagrams, illustrative of the archetypal 

 form of the Mollusca and its more important modifications. 



The shaded portion is the hsmal surface, the unshaded the neural surface. 

 Figs. 2 and 3 are supposed to represent the development of an abdomen, and the changes of 



position thence undergone by the intestine and heart. 

 Fig. 4 is a diagram of a Pteropod, corresponding with fig. 2. 

 Fig. 5 is a diagram of a Cephalopod, corresponding with fig. 3 ; but in these, changes in 



the different parts of the foot have been also effected. 

 Figs. 6 and 7, similarly are supposed to represent the development of a post -abdomen. 

 Fig. 8. A diagram of Aplysia, corresponding with fig. 6. Atlanta corresponds exactly 



with fig. 7. 

 Figs. 9, 10, II, are imaginary sections of a MoUusk, a Fish, and an articulate animal, re- 

 spectively, to show the relations of the nervous, alimentary, vascular, and 

 appendicular systems. 



The Mollusk and articulate animal are in their normal position ; the fish is 

 turned upon its back to correspond with them. * The pectoral fins, f The 

 legs of the articulate animal. 

 Figs. 12-15. The buccal apparatus or tongue of Patella. 

 Fig. 12. From the right side. 

 Fig. 13. From above. 

 Fig. 14. The supporting cartilages. 

 Fig. 15. The elastic plate which plays over them. 

 Figs. 16, 17. The stomach of T'/erofifraj. 



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