THE MESOZOIC AGES. 225 



seizing a few mouthfuls, returns sullenly to the 

 surface. A great number of species of Belemnites 

 and allied animals have been described; but it is 

 probable that in naming them too little regard has 

 been paid to distinctions of age and sex. The 

 Belemnites were for the most part small creatures ; 

 but there is evidence that there existed with them 

 some larger and more formidable cuttles ; and it 

 is worthy of note that, in several of these, the 

 arms, as in the Belemnites, were furnished with 

 hooks as well as suckers, an exceptional arrange- 

 ment in their modern allies. It is probable that 

 while the four-gilled or shell-bearing cuttles culmi- 

 nated in size and perfection in the Ammonitids of 

 the Mesozoic, the modern cuttles of the two-gilled 

 and shell-less type are grander in dimensions than 

 their Mesozoic predecessors. It is, however, not a 

 little singular that a group so peculiar and appar- 

 ently so well provided with means, both of offence 

 and defence, as the Belemnites, should come in and 

 go out with the Mesozoic, and that the Nautiloid 

 group, after attaining to the magnitude and com- 

 plexity of the great Ammonites, should retreat to 

 a few species of diminutive and simply-constructed 

 Nautili ; and in doing so should return to one of 

 the old types dating as far back as the older Palae- 

 ozoic, and continuing unchanged through all the 

 intervening time. 



The Crustaceans of the Mesozoic had lost all the 

 antique peculiarities of the older time, and had so 



