228 THE CEPIIALOPHORA. § 202. 



dc Tordre des Opisthobriiiiehes (Milne E(hyart!s), Tectibranclies, Nudi- 

 branchcs, Inferobrunclies (Cuvier) ; Ann. d. Sc. Nat. IX. 1848, p. 172, XI. 

 1849, p. 74. 



Alder and Hancock. A Monograph of the British Nudibranchiate Mol- 

 lusca with figures of all the species. Part I. 1844. Part V. 1851. Un- 

 finished. [This fine work contains very valuable anatomical details and 

 includes Hancock's contributions upon these animals given also iu the Ann. 

 of Nat. Hist.] 



On the Anatomy of Oithonia, in the Ann. of Nat. Hist. IX. 



1852, p. 188. 



HaiKoch and Embleton. On the Anatomy of Eolis (Contin.). Ann. 

 Nat. Hist. 1848, I. p. 105, also 1849, III. p. 18.3. 



Hancock. On the olfactory apparatus of the Bullidae. Ibid. IX. 1852, 

 p. 188. 



On the Anatomy of Doris, iu the Philos. Trans. 1852, Part 



11. p. 1. 



Sovleyet. Memoire sur le genre Acteon d'Oken, Journal de Concholo- 

 gie, 1850, No. I. p. 1. 



Leidy. The Terrestrial air-breathing Mollusks of the United States, &c. 

 Described and illustrated by Amos Binney. Edited by Aug. A. Gould, 

 M.D. 2 vol. Boston, 1851. Special Anatomy by Joseph Leidy, M.D. 

 [For beauty of execution Leidy's drawings are unsurpassed.] 



Leyd/g. Ueber Paludina vivipara : im Beitrag sur naheren Kenntniss 

 dieses Thieres in embryologischer, anatomischer und histologischer Bezie- 

 hung; in Siebold and Kolliker's Zeitsch. II. 1850, p. 125. 



Anatomische Bemerkungeu iiber Carinaria, Firola und Amphi- 



cora. Ibid. III. 1852, p. 325. 



Karen and Damelssen. Bitrag til Pectinibranchiernes Udviklingshisto- 

 rie, Bergen, 1851, or its Transl. into the French, in the Ann. d. Sc. Nat. 

 XVIIL1852, p. 257. 



Gegenbaur. Beitriige zur Entwickelungsgeschichte der Landgastropo- 

 den, in Siebold and K6lliker''s Zeitsch. III. 1852, p. 371. 



Bau der Heteropoden und Pteropoden. Ibid. IV. 1853, p. 



334. 



Moquin-Tandon. Histoire naturelle des MoUusques terrestres et fluvi- 

 atiles de la France, 1847, avec un Atlas de 25 Planches, &c. Anatomie 

 de Ancyle fluviatile, in the Jour, de Conchol. 1852, No. I. p. 7, No. II. p. 

 121, and No. IV. p. 337. 



Rang and Souleyet. Histoii-e natui-elle des Pteropodes, Paris, 1852. 



CHAPTEB I, 



CUTANEOUS SYSTEM. 



§ 202. 



The cutaneous envelope of the Cephalophora consists of a dense dermis, 

 of a cellular structure, often containing pigment matter which is free 

 or in cells. It is covered with a delicate ciliated epithelium, which, with 



