164 MEDITERRANEAN PROVINCE. 



seasons, and some are very generally supposed to 

 migrate periodically from south -to north and back 

 again. The successive appearance of numbers of 

 Loligo vulgaris, Sepia officinalis, and the little Sepiola 

 along the coast of France and later on ours would 

 seem to confirm this notion. These habits deter- 

 mine the distribution of the Cephalopods over the 

 Mediterranean area ; the forms that occur there 

 are wholly Atlantic ones, and from the western 

 entrance to the central and thence into its extreme 

 eastern portion, the number of species decreases 

 progressively. As far as the Cephalopoda are con- 

 cerned, the Western Mediterranean has fewer forms 

 in common with the Eastern than it has with our 

 south British seas, the reverse of what takes place 

 as to the other Mollusca. Philonexis, Cranckia, 

 Loligopsis, and Cheiroteutliis are amongst the more 

 peculiar forms of the Lusitanian and West Medi- 

 terranean province. Some forms which occur on 

 the West African coast, such as the Argonauta 

 hians, have not yet been noticed within the Straits ; 

 yet this species lived in the central Mediterranean 

 area during the later tertiary period. 



The known species of Cephalopods may be taken 

 at about 110 ; of these, fifty occur in the Atlantic ; 

 the " eight-armed " Octopus, and the " ten-armed " 

 jRossia, Sepia (cuttle), Loligo (squid), Onycoteuthis, 

 and Ommastrephes, are met with in its cold, tempe- 

 rate, and warmer regions, but the latter are richest 

 in specific forms. Argonauta, Philonexis, and Se- 



