52 AFFINITY OF THE TRILOBITES, ETC. 



1. That these animals moved only by swimming, that they remained close beneath the 

 surface of the water, and that they certainly did not creep about at the bottom, as Mr. 

 Klöden supposed.* 



2. That they swam in an inverted position, the belly upwards, the back downwards, 

 and that they made use of their power of rolling themselves into a ball as a defence against 

 attacks from above. 



3. That they lived on smaller water-animals, and in the absence of such, on the spawn 

 of allied species. 



4. That they most probably did not inhabit the open sea, but the vicinities of coasts, 

 in shallow water, and that they here lived gregariously in vast numbers, chiefly of one 

 species. 



.5. That the number of species could never have been very great. This is indeed 

 proved by the mode of their appearance in the fossil state, inasmuch as scarcely more than 

 six or eight species have been found together anywhere in one stratum. 



6. Although the number of species has not been large, the number of individuals 

 was very great indeed ; a fact likewise observed in the living P/ii/Uopoda, of which we as 

 yet scarcely know a dozen species, although these are grouped into about six different 

 genera. « 



7. The great differences existing in the dimensions of the present P^y/Zo/JOf/'? according to 

 their age, justify us in expecting such differences also among the Trilobites ; and very large 

 individuals of the latter, therefore, do not indicate a separate species, unless other differences 

 are presented. 



* See 'Verst. d. Mark Brandenburg,' vou H. Klüdeii, p. 104. 



