DESCRIPTION OF PLATES. 



PLATE V. MOLLUSCA AND CONCHIFERA. 



Fig. 1. Loligo vulgaris. The Cuttle-fish. 



2. Nautilus Pompilius. 



3. The same shell cut to show the divisions. 



4. Conus generalis. 



5. Voluta musica, cut to 'show the whorls of the pillar. a, 



the plaits of the pillars or columella. 



6. Cyprsca exanthema. 



7. Buccinum undatum. a, the whorl of the spire. 



8. Dolium galea. 



9. Rostellaria pes-pelecani. 



10. Murex erinaceus. 



11. Trochus zizyphinus. 



12. Scalaria pretiosa. The Wentletrap. 



13. Nerita peloronta. a, outer lip. b, inner lip. 



14. Lymnea stagnalis. 



15. Planorbis corneus. 



16. Chiton marginatus. 



17. Helix arbustorum. 



18. Area Nose. a, the umbo, or swelling of the beak. b, the 



hinge, with its numerous teeth. 



19. Pecten Jacobaeus. 



20. Cytherea exoleta. a, the breadth, or transverse diameter. 



b, the longitudinal diameter. c, the posterior de- 

 pression. * 



21. Tellina radiata. a, a, muscular impressions. 



22. Mactra subtruncata. 



* The right and left sides of a Univalve shell are ascertained, according to Lin- 

 nseus, Lamarck, and others, by placing the shell erect with its opening to the ob- 

 server ; while Draparnaud and Blainville place the shell obliquely on its mouth, 

 with the summit behind and upwards. In both cases the terms right and left side 

 are applicable to the same portion of the shell. In Bivalve shells, Linnaeus, Lamarck, 

 and others, place the shell on the beak or summit with the opening above and the 

 ligament before ; while Blainville and others suppose it placed on its edges, and the 

 ligament between the summits and the observer. The vertical diameter in this case, 

 or from the ligament, is the length of the shell according to Linnaeus and Lamarck, 

 and the breadth according to Muller ; and a line at right angles to the perpendicular 

 indicates the transverse diameter. That part of the shell in which the ligament is 

 placed is generally termed the anterior slope ; and the posterior slope is the direction 

 of the shell on the opposite side. 



