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Show 22e EXPLA.N ATJONA . d lf ~ate tn trusting to the work of Agas~Iz,, I deen:e m.yseuirer and ingeniou~ the report of this Industnous InC} ubllshed. I-Iow writer whose volume was then newly r d affmity ;ecent' the contradiction of t~e .~11~1-su~p~~~. but the may be, or what faith to place ln I ' l{~O retend's in this reader will probably hold on; who o~al ~T-iter e'xcused, instance, to the char~ct.er o. a gene osito; of phys .. when he shows so dishn~t.y1shed r:nr!~!ntly countenan· iolo~y as Dr. Carpenteib' sd~ mfofishes ,, says he ,, are · '- 'd " The o Ies o ' ' cwg the I ea :- . s or lates whic.h have somee usually covered With scale d phich 'in some species of times a bony hardness~ an . \\ 'ear to have been of fish that.do not ~ow 1ex~~;-~~v~~ ~a\re a sort of tra'Y!'sitimt. the dens1ty of ename · .r h invertebrated anunal.~; to the external skeletons 0J t e [· tly find the in- . h' 1 lso we not un requen and 1 n t 1s c ass, a d 'fi . ... t . the stony matter from tcrnal skeleton. so . ~ ~~nd 1 ~s that it seems like catwhich bone.denves ~ 9 . ar /~of the lowest species, we tilage or gnstle ; a~ .In t v:rtebral column; so that the do not even find a dl~b nc th vertebrated to the in vertechange of .cha~·acter rom e not an abrupt one, and bl'ated senes IS a gradual, c:nd . d al if we were would. probably be foun~ st~\\ ~~~·ef~I~~su of animal li!e • acquainted, no~ only wlth th which have existed In which now exist, but a so o~e t' ~ " b d are now ex 1nc-. ages long gone y' an t . l t s to the general fact of the The above a!gumen ~e a e It is necessary, also, to first fishes belng placolidean.h ld be no fossil remains meet th. e I· nqun· · y w. h. y t 1.e re s thoeu lower animals to fi s h · indicatu~g a transilt Ionffi o~ ntly discovered cestraceon The revwwer spea {S o a ~ece 1. d "Such " he exbelow any other fish-beds In bEngt. an ·r..r )I'ts" :, vVe en- . t . ' first a or lVe euc . . c' laims ' " are dn a u" ie s good natura1 1' s t we1 1 to consider treat," he ad s, any. d t 11 us whether they do n?t such facts as these, aa e t t derive such orgamc utterly demolish ev~ry ~ttemlp of animal life found in structures from any Infenor c ass o d sess the crescent-shaped head, and ic; more elongated, but both pos 'ointed bodv. They illust.r~te a • l)Oth the angular an~ a:pparently J a meet. They exh1lnt the rnirallly how two distinct t orc~;:h~h~ plated fic;h is linked to t!l.~ . joints, if I may so speak,~ t: ~occosteus is a sti:\ge further on' ,ld shelled crustae P-an. Now . e. ace halaspis with a scale·covere is more unequivocally a fish; Jtl~ a~d tl1e h~rns of the crescent tail attachcu to th~,~11 1)~~R~; ldndstont, p. &4. shaped head cut ou. I'OSSILS OF OLD RED SANDSTONE. 229 the older strata?" Now I cannot tell what good naturalists may say in answer to this appeal; but I feel, fo: my own part, that the facts in question-as far as they can be admitted to be so-have no such destructive effect. In the first place, the cestraceon Is only one of those cartilag;ines, the real character of which had just been explained. It is not the lowest of its order, but neither is It the highest. So fur from this being the case, the respiration of the whole family (Selacii, Cuv.; Plagiostomi, Desm.) to which it belongs, and which als9 includes sharks, is performed in a manner which approximates these fishes to the worms and insects-namely, "by numerous vesicles called internal gills, the entrance to which is from their gullet. while the exit is in general by corresponding apertures on the side of their neck;"* other fishes having free gills, marking a high organization. The sub-divided form of the stomach-the absence of that concentration, which is, perhaps, the most enlphatic mark of animal advancement-belongs to this family alone amongst fishes, as it does to the lowest farnilies of several of the higher orders of the vertebrata. Thus, the cestraceon is, on many considerations, a low fish, though certainly possessing some traits of superior character, and not the lowest of its order. In the second place, I would protest against any inference unfavorable to the hypothesis of development being drawn from a discovery so new, so isolated, and in a branch of inquiry so extremely unsettled. At no time during the last ten years have we had, for a twelvemonth at once, stable views respecting the initiation of fishes. Lately-so lately that part of my book was written at the time-the lowest were understood to be some of a minute size, immediately over the Aymestry limestone, in the Upper Silurians.f Now we have a cestraceon announced to us at a lower point in that formation. But how far it is likely that our information is to rest at this point the reader may judge, when he hears of M. Agassiz an. 1\. nouncing, within the last few months, that, though acquainted with seventeen hundred species of fossil1ishes ~ FlC'tc.her's Physiolog.y , part i., p. 20. ' t ·'The minute and curious fishes in the uppermost bed of the Ludlow rock are the e'],rliest p1·ec1wsm·$ of many singular ichthyolit€' s whieh Ruccced in that enormous formation the Old Red Sandstone."-Mtwchison's .llddTess to the Oeological &~iety, Feb rua.rT, l S..t-2. J ' |