58 
THE GEOLOGIST. 
The Australian and Tasmanian carboniferous rocks have also 
afforded their quota of common species, for although the forms from 
those continents have not been sufficiently examined, still from a 
passing glance I have given to collections sent home from Bundaba, 
and Poi-t Stephen in Australia, as well as from Van Diemen's land, 
I have already been able to recognize T. hastata, SjJ- striata, Sp. 
glabra, S. lineata, Eh. pleurodon, Strept. crenistria, Orthis Miclielini, 
Prod, cora, etc. If again and by a rapid stride we should find ourselves 
cast on some of the Spitzbergian frozen coasts, we may there 
pick up several of our common species, such as Sj). odoplicata, Strept. 
crenistria. Fro. sernireticulatus, P. costatus, etc., along with other forms 
not known in Britam, and lastly, not to extend the limits of this paper 
beyond reasonable bounds, should we visit the prodigiously extended 
carboniferous regions of America, we shall there also find a vast per- 
centage of species identical mth our own, but which in many instances 
are still hiding their true characters under the disguise of borrowed 
names. Possessing as I do a very extensive series of Ameri- 
can Carboniferous species, and for which I am indebted to the 
kindness of Mr. Worthen, as well as to that of some other American 
geologists, and having compared these with our British species and 
specimens, I may mention from among others not yet sufficiently 
studied, the following few as being identical with our own ^S'. 
saccidus, Atlujris amhigua, A. suhtilita, A. plano-sidcata, A. lameUosa, 
A. Eoyssii, Eetzia radialis, Spirifera striata, S. hisidcata, 8. lineata, 
S. Urii, S. odoplicata, Eli.plettrodon, Ortliis Micliilini, Strept. crenistria, 
Prod, cora, P. pimctatus, P. longispinus, P. semireticidatus, P. scahri- 
cidus, P. costatus. Crania quadrcda, Piscina nitida, Lingida mytiloides, 
etc. 
This rapid but convincing proof of the existence and distribution 
of many characteristic British species all over the world where con- 
temporaneous carboniferous rocks have been deposited, should inculcate 
upon us the absolute necessity of carefully examining and re-examining 
our species, so as to avoid the unfortunate results that may ensue 
from arbitrarily narrowing their limits of variation — thus violating 
the law of natm^e, as well as retarding the advance of science.* 
Much indeed may be expected from the rising generation of young 
naturalists, who, unprejudiced and unlettered, may work out for 
themselves a new path ; and by seeking to determine with more 
attention than has hitherto been done what are the resemblances that 
exist between so-termed species, may be able to trace and connect 
those modifications that have been produced by time and circumstances 
* Darwin considers tlie term species as one arbitrarily given, for tlie sake of 
convenience, to a set of iadivicluals closely resemblrag each other ; and it does not 
effectually differ from the term variety, which is given to its less distinct and 
more fluctnating forms : that the term variety, again, in comparison with mere 
differential differences is also applied arbitrai-ily, and for convenience sake ; that 
no one can draw any clear distraction between individual differences and slight 
varieties, or between individual differences or more plainly marked varieties, or 
sub-species or species. 
