368 Termination of the Paleozoic Period, §c. 
The previous remark with regard to the blending of adjacent 
strata, and the prevalence of some characteristics of one era in the 
the mesozoic strata. 
Only a single fossil fish is known common to the Permian and 
inferior systems, and that not lower than the Carboniferous ; i. @ 
Palaoniscus Freislebeni, which occurs both in the Permian and 
Carboniferous systems, but not in the Devonian and Silurian. 
But three Gasteropoda are cited as common to the Permian and 
inferior systems, and two of these are problematical ; i. e. Loro- 
nema Urii and L. rugifera ; the former, perhaps, common to the 
Permian and Devonian systems. ‘The third, the Pleurotomaria 
carinata, is given as common to the Permian and Carboniferous 
systems. 
Only one of the Monomyaria, i. e. Avicula antiqua, 1s common 
to the Permian and inferior systems, being found also in the Car- 
boniferous. 
All the species of Dimyaria are peculiar to the Permian. On 
the whole, therefore, very few even of the mollusca are common 
to the Permian, Devonian and Silurian; and when we recollect 
that this class of animals is capable of surviving very great VICIS- 
situdes, it cannot be considered extraordinary that a few may 
have escaped and outlived even a great change of temperature, 
or some sudden catastrophe. Fi 
boniferous group, whilst a similar want of conformity e pareille 
discordanté”) is very rare between the Permian and ‘Triassic. 
