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Show 226 EXPLANATIONS. of thern belong to fan. 1lies now living in our seas." He instances a cestraceon-a high kind of placoid-recently found in the Wrnlock limestone, a low portion of the Upper Silurians, and therefore near the beginning of fish Some of the ganoids, also, of the Old Red Sandstone n1ake an approach to a higher class-reptilia. Besides the usual row of fish-teeth, they have an inner range, in vvhich we see the form of those organs among the sauria. It appears, in short, according to this writer, that the fur· ther back we go among the fishes, we find them possessed of the higher characters. Of the real character of all this hardy assertion I shall enable the reader to judge. The fishes of this early age, and of all other ages previous to the chalk, are for the most part cartilaginous. The cartilaginous fishes-Chondropterigii of Cuvier-are placed by that naturalist as a second series in his descending scale; being, however, he says, "in some measure parallel to the first." How far this is different from their being the highest types of the fish class, need not oe largely insisted on. Linnreus, again, was so impresse0 by the low characters of many of this order, that he actually ranked them with the worms.* Some of the cartilagi!lous fishes, nevertheless, have certain peculiar features of organization, chiefly connected with reproduction, in which they excel other fish ; but such features are partly partaken of by families in inferior sub-kingdoms, showing that they cannot truly be regarded as marks of grade in their own class. When we look to the great fundamental characters, particularly to the framework for the attachment of the muscles, what do we find ?-why, that of these placoids-" the highest types of their class ! "-it is barely possible to establish their being vertebrata at all, the back-bone having generally been too slight for preservation, although the vertebral columns of later fossilfishes are as entire as those of any other animals. In many of them traces can be observed of the muscles having been attached to the external plates, strikingly indicating their low grade as vertebrate animals. The Edi~purgh reviewer's ''highest types of their class". are! ID rr.alit~, a separate series of that class-generally 1nfer10r, • Dr. Fletcher places the Chondropterigii lowest in a seal• which takes as its criterion ''an increase in the number and extent of the manifestations of life, or of the re. ~tions which an organ ized btiing bear& to the external world." FOSSILS OE" OLD RED SA".1''."" D STONE. 221 taking the leading features of or . . cr!teri~n? but, when details of~~~IZD:ho~ of s~ructure as a etretclung further both downwardanizatwn aJ e regarded, other series; so that lookina- t and upw~rd than the much entitled to cali them th: lone e~tremtty' we are as looking at another extremity is towesli t~ the reviewer, of their class. Of the encr~l i 0 .~a. em the highest rootn for doubt Theil~ carfl ?feuor•ty there can be no first place, anaiogous to the ~~~l~lOu~ structure is, in the animals in general.* The ~axi\)~1~Ic state. of vertebrated bones are in them rudimental ThY. a~~ Intermaxillary the under ~ide only, an admitted fe:tir. a es are finned ~n a? embryo tic stage; and the m th . UI1e of the salmon 1n Side of the head also a ou IS p aced on the under of structure. These char~~:;~ aa~·~ embry.otic feat.ure portant, whatever the Edinburrrh ~s~enhal and Im· the contrary; they are the char~ct ~evww~r may say to I am chiefly concerned in lool . eis, which, above all, tures of embryotic ro ress nng to, for. they are fea .. the grand key to uie fheory ~~~ en\bryohc progress is fore throw back to my reviewer theve ~pment. I there" clung to feeble analogies," and ,;kc arge that .I have broa~ and speaking facts of nature" ept out of VIew the With regard to the alle ed f: 1 .. character of some of these% h a stt~ of t~e crustacean peating the blunders and s es, an the discredit of res servers, before any good evfd~e;ses ma~e ~by the first obonly S?Y that, at the time wheC: ~as b~ ore them, ~ can ~~ologists and inquirers into fossily. h ok was Written, highest character were writing b{~ l thyology. of the of the cephalaspis and cocco t' pu Icy and privately, between the crustacea and fi h s t~ua as . apparently Jinks lattrr animal beinrr particul~ri ~ Yerhcal mouth of the eating the intermediate charact!t· Clt1d as a feature indicalls "the excellent work of ou: n.wh!it the reviewer countryman" Mr H h M"ll 1 mentonous self-tauo-ht w ' • urr I er pub!" h d . o apparently crustacear:. o charactei! of t1s e filn 184.1, the peatedly referred to t Not h . ese shes IS re- >~- Cartilage " · . . aving access at the time to In the earl·y s' tatem o fm tahney haummmaanl s~ fo rms t.l l e enh·r e structure. and penle,·'s General Physiolo~y p 37 mbryo lt does the same."-Cm· t Mr. Miller calls upoll ili~ rdaders t " . cephalaspis, or buckler-head a fi h f o mar.t the form of tho which the remains of the trllob·~ o the formation over that in he says, "the fish and crustacea~ E>~ mos,t abdou!Jd: He will find,' re \\on erfn}. y alike: the fish |
