228 THE CEPHALOPHORA. «§, 202. 



de I'ordre des Opisthobranches (Milne Edwards), Tectibranches, Nudi- 

 branches, Inferobranches (Cuvier) ; Ann. d. 8c. Nat. IX. 1848, p. 172, XI, 

 1849, p. 74. 



Alder and Uancock. 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 uninials given also in the Ann. 

 of Nat. Hist.] 



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



1852, p. 188. 



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

 Nat. Hist. 1848, I. p. 105, also 1849, III. p. 183. 



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

 p. 188. 



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



II. 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.] 



Leydig. Ueber Paludina vivipara : im Beitrag sur näheren Kenntnis» 

 dieses Thieres in embryologischer, anatomischer und histologischer Bezie- 

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



Anatomische Bemerkungen über Carinaria, Firola und Amphi- 



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



Koren and Damelssen. Bitrag til Pectinibranchiernes Udviklingshisto- 

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

 XVIII. 1852, p. 257. 



Gegenbaur. Beiträge zur Entwickelungsgeschichte der Landgastropo- 

 den, in Siebold and KöUiker''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. Histoire naturelle des Pteropodes, Paris, 1852. 



CHAPTER 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 



