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Show 224- EXPLAN A 'I 1o.NS .. d d crustacea (era s, &c.,) ders, we do not hnd any e~ape o~s ·ever othe~ mollusks thouo-h these could have hved .w. el tv ar <1 most cle .. and ~rustacea could. In .fact, It IS a ~a~" that Mr. Lyell fective development of ltfe; so m~~ B~·a~hiopods, with calls it par excellence, the Age lt d bi·..,,al-ve shell-fish ' th b ·means exa :e ' reference to ·. e Y no . t l · Such being the ac-which forms 1ts predomwan c ass .. t · desct·ibinO' even tual state of t h ~ case, I m. ust pers1sw 1knn ow w• as noo t the the fauna of "this age, '~~ICh we ~~n humble exhibition first as, generally spea ong, su? ht ex ect upon the de-of the animal kingdor~ ~ ~ea:~arly sfaO'e ~f the history velopment theory' to ln a o . of organization.* h f}j er Silurians, where ne\V spe- W e now eo me to t e . pp ear besides a few ob-cies of invertebrated 3:nl~:l~p~e~radce, according to the scure fishes. fhere 1} transition from the fortner sp~Edinburgh reviewer, o t ~ s he know the signs by whten cies to the ~r~sant; bub o~ tected? I am aware of no~e. such a transition could . e e sharply defined, that IS, He says the new spectes are be without any preju· strongly distinct; and .so they may as far, at least, as I undice to the transmutatwn theory ·l s th,.,t there are the . A d here he remai { <.4 • th derstand It. . n. f this theory "both 1n e same difficulties ln the way o , th have in the eagerness of ,. Objectors to the devel~pmen~ es~~~es on' the subject of the counter-theori7.ing, commt~~dh \~e~ will yet feel to be e~tremely Silurain fossils, in a w/aBy '~t' 1~ Review we havP. seen placmg even wkward The No,·t t n. ts unding this statement upon ~ h sin the fir·t fossiliferous rock~, gr~ d for fully eight year~-a s :uthority which has been a~tl~ua e 'rhe B1·itish Qtta?·terty R~· ~~st period in the history tof g~oT~i~,Y Author's theory," says t~•: view is equally unfortuna e. . ls should be the lowest In 1 . 'ter "requires that these a·ruma t fish with its back-bone, ~~le 'But no argnment can conve~u:cular: systems, into an an· o.nd highly develop.ed !ler;,o~s a~he do matic allegations ~f the imal of low Ol'~·lll1Zaho~i1·~·)point are s~fticien~ly expflsd~ 1; ~: ~~~bn~ v~·~~~;~~ ;~~e~ !~:~:r':."'i;:~r~~~~;;~; t~! fi;st '~;~i~' Whewell parbcipatm::> I 1 In the preface to a vol~me .1' the the above-mentioned journa s. d r the title of Indicatwns nJ • w be has recently published, un c 'th a crucle and incorrect vtet . h meets my argnm(~nts WI. . tence-" Vertebrae ?r·:~~:~~~l .~~,~~~~· ~~~ ~i~~~~~~ r;~~:~hr~·r ~ ~~c~;~re!~~e~~·; i;~m [that of devclopm.ent] exc~~e~ un~n~wn to him. Many a~· non·pic;;ciferons format~~~ ~~~elopm.,~tt theory, in obscurer qu the objections madefto . e ·ta.r kind. ters, rest on errors o a Slffil UPPER SILURIAN FOSSILS. 22b grou1 ing of each separate system, and in the passage from one system to another; and that is true, whatever part of ._lie ascending geological series we choose to take between the lowest formations and the highest.,, As he does nor state the nature of the difficulties, I cannot undertake to say what argument or what reconstruction of my system may be necessary to meet the1n. Till we are more clear, l1owever, regarding the actual affinities of animals, I would suppose that any judgment as to difficulties in their grouping in geological formations, or succession in different formations, might well be given son1ewhat less dogmatically than they are by this writer. The few fish-remains of the Upper Silurians may be associated with the ample development of this class in the next (Devonian or Old Red Sandstone) system. They belong to Agassiz's two orders of placoids (these by them .. selves in the Upper Silurians) and ganoids, the former of which are represented by our sharks and rays, the latt~r by the bony pike of America and the polypterus of the Nile. Such are the only fishes found .till we come up to the chalk formation, when the now-predominant orders of cycloids and ctenoids begin.* The Edinburgh reviewer makes a strong point of the placoid and ganoirl orders, as unfavorable to the progressive theory. "Taking into account," he says~ "the brain, and the whole nervous, circulating, and generative system, the placoids stand at the highest point of a natural ascending scale, and the ganoids are also very highly organized." Of certain families of the first order, found in the Old Red Sandstone of Russia, he says, " Let the reader bear in mind that these fishes are among the very highest types of their class, and that we can reas·on upon them with certainty, because some Y. The North British Review presents as a strong objection that "several new ctenoids, which had been found only in the carbo. niferous system, have been discovered among the fishes brought by Mr. :vrurchison from the Old Red Sandstone of Russia. Resolved to make out his position, the author asserts,~' &c. This is an unlucky venture in opposition. The critic evidently meant it to have a very damaging effect, in consideration that the ctcnoids are osseous fishes. The fact is, that the fishes brought home by Mr. Murchison are not of the ctenoid order, but belong to a placoidan family called Ctenodus. The mistakes made by this writer, in the geological part of his paper, are of a very grave kind, yet only such as many men of scientific eminence may be expected to make w!1eu they venture out of their own peculiar de!lartment, and rashly under-estimate the strength of the arguments to which they arc opposed. 18 |