Page:Encyclopædia Britannica, Ninth Edition, v. 10.djvu/353

Rh siLUin.i.'.] II I. Luzcrr S[luri'an— (w) liorkliolin linicstones and inarls (IIaIIi/sites] /ub_r/riu//1 [cu.., Ilclio/z'tr's 'mcgastom((, Sy'rz'n- _I/')[I]l,_l/lllllll. orgmimn, Lie/ms mar_r/rLrz't{fcr, 1’[czu-orlig/mlms digitcrus, Orthoccms cala- mitcum, &e.) .................................... .. (1)) Lyekliolin, yellow or grey compact liiiie- stoiie and nnirls (0rtIu's _/labclluluuz, 0. .-'11.-/o;u'«c, 0. 1'/zsuluris, &e.). . . . . . . . . . . . . . . . .. (H) Weseiilin-i'g limestone and niarl (lirt/(is /cs-tiI¢li'/Lrzritt, 1;':Lcr£nm°us muItisrgnzciz- | /ulus, Liv/uts I;'t'«-/ucaI:li', &e.) ............. ..J (c) Liinestoiie usually somewhat bitiiniinous,) with partiiigs of reddisli yellow and brown very bituininoiis inarl (L'r'_r/n.':-Iu'rL cum- yzlicuta, 4-lsupluts uczuni/mlus, Orl/zis culli- 5//uutuul, Lrplu-Im s:_'r£r'c:_(,. . . . . . . . . . . . .. (bl Oi'tlioeeratitc. limestone. and in-.u'l bands, 13 to 40 feet thick(.lﬂuIl[cuZ1))0ru ]ir't/'0- jmlilmm, 1:1-/u')m.9)'»IzIrrilr-s ailrrmtiiun, _-Is((p/(us c.rpu.u.s-us, Uri/1 is ralli_r/rumnut, I/rt/wccrus 'ru_«/hmtuui, ................. .. (If Liinestmie, full of glauconite grains, especially towards the bottom (rl/u's ow/11';/ruuinirt, O. 0.:-triisrz, abundant frag- ments of I1/tcims and A.9(q)/ms, &e.)........J (:7) ttlaiieonite sand (6 feet), with nunicrous) l"oi'ainiiiil'ei'a in the glauconite grains (P112117!)/'I.’”/(, l.'_r/nibulirt, T1'r‘(lcm(mnz'((,&c.) and the “Conodonts ” of I'ander .......... .. (I-) _-tluin-slate (10 feet), highly carbonaceous, with pyrite-iio_diiles and abiind:iiit grapto- lites (l)1':_'tII/unrrmra II [.s[n._rV)'¢', 1/ulus, &e.) (71) Ungulite sandstone (120 feet), yellow to white, with (in the upper part) abundant shells of Obulirs Jpollinis (“ Ungulitcs” of I’ander) ...................................... .. (H ‘ lllue 4-lay, with sandstone bands, sparingly thssililt-i'oiis; bored at ltevel to a depth of 800 feet without its bottom being reachcdl - = Caradoc. I = Llaudeilo. t = Arenig. In the centre and south of Europe by far the most important .'iliirIi-aii area the basin of l";i)llL'llil'.l, soIadmirably worked out by ll. I);11'1':ll1I_l(3 in his great work already cited (p. 3:23), wlicrein the 1'-;»i'iiiatioi1s are grouped as in the subjoined table :— Iiltage II Shales with eoaly layers and beds of quartzite (I’/iacops fCClUl(llL.S', Trntucu- Ii/rs clc_t]:I/ts), _with species of _ Lrptugna, U1‘,/It/JC-'}'I(.5‘, 1.:/rules, (1'U/llftltlts, KIT.  8o0 ft. H -rgillaceous liinestoncs with cliert, .'<ll:1lt-s, and L':llI'tll'C0tlS nodules ....... ..1000 ,, iuinerous trilobites ot the genera ])rrl- uuuu'/cs, L’ro:z(c1(s, I’/zacops, I’roc'tus Ilm-):cs, and Cll.l_IjI)l/JILF; .UI'1/1)(L)'(.‘tiCI I:u'i.s-, [’cn.‘¢mic)'u.9 Iinqiufcr. F l’ale and dark limestone with cliert. I[au'pr’s, Liclms, I ’/mcops, Atryprr reticu- /urz'.s', I’:')ztan1m'zts gulcatus, Fur0s1'tcs f.'uI/¢/anrlica, I". ﬁbrosa, Tcntaculitcs. E Sh-ales with calcareous nodules, and shales resting on sheets of igneous rock (300 ft.) ._ ............... .. ...... ..450—900 ,, A very rich Upper Sili_irian fauna, abundant eeplialopods, trilobites, &e.; Ilulg/sites eaten ularius, graptolites man y K species. I) Yellow, grey, and black shales, with quartzite and_congloinerate at base .. 3000 ,, -ibiiiid-aiit trilobites of genera Trina-
 * ,-_7cus, Oyg/Iyiu, x18((1I]tl(S, I llccims,

1Iri:101)lciz)'[dc'.9, &c. C .'hales or "sehists,’ sometimes with porpliyrics and eongloinerates ...900—1200 ,, Pu)'r((Zo.'rz'zlcs, ]L'”l:[').S‘0('('[1].I(lI u_.e, -1_r/Iwstus, and other genera of trilobites rel'erred to above (mite, p. 3230). Upper Siliirizin. __ __I _ 3d l"aun:1. .., Lower Silurian. ..d "'aiina. I,__ .a..Tl,__ - l’riinordial _, Fiiiiiizi. ,, B I Sehists wholly iinfossilil'erou.<; resting A S on bottom gneiss. Azoie. C'ainbrian. ~.f-§/ The lower two c'tugr.9 (A, B) eori'espoiid probably to seine of the older parts of il](‘rlll'itl.s‘ll (‘ainbriaii series, and perhaps in part to still older rocks. Etage C, or the l’riniordial Zone, is the equivalent of the Upper Cambrian rocks of 'ales, possibly also pai'tly of the Areni_'_»; series. Etage D, subdivided into tive groups ((Z1, (Z2, (I3, (Z4, “’_“l ((5). ﬂD1i0fl1‘S to be, on the whole, rcpieseiitative of the Lower Silurian formations of the British area, though it is impossible to make the minor subdivisions in the two countries agree. The GEOLOGY 33$) remaining four formations answer to the English and Welsh Upper Silurian series,——the highest zone of all (H) indicating by its organic remains the approach of the Devonian series. Sinall though the area of the Silurian basin of Bohemia is (for it measures only 100 miles in cxtrcine length by 44 miles in its greatest breadth), it has proved extraordinarily rich in organic remains. il. Barrande has named and described above 2000 species froin that basin alone, the greater number being peculiar to it. Sonic aspects of its organic faeies are truly remarkable. One of these is the extraordinary variety and abundance of its straight and curved ceplialopods. ll. Ilarrande has deterinined 18 genera and 2 sub-geiicra, comprising in all no ft-wt-1' than 1127 distinct species. The genus Urt/zoccras alone contains 554 species, and C'_I/rtocrras has 330.1 The trilobites likcwise appear in great iiuinbers, the saint- indefatigable explorer having detected as many as 42 distinct genera, coniprising 350 species. Of these the most proliﬁc genus is Jjronlcus, which includes 46 species entirely confined to the 3d fauna or Upper Silurian ; Aci¢l¢(s))z'.9 has 40 species, of which 6 occur in the 2d and 34 in the 3d fauna. I’raé‘tus also l1'.1lnl)('1'S 40 species, which all belong to the 3d fauna, save ‘.2 found in the 2d. Other less prolitic but still abundant genera are 1Jalmanitcs, 1’hacop.9, and 1[[tL'ILll.S‘. The 2d fauna, or Lower Silurian rocks, contain in all 32 gtiieia and 127 species of trilobites, while the 3d fauna, or Upper Silurian forniations, contain 17 genera and ‘.205 species, so that generic types are more abundant in the earlier and speciﬁc varieties I in the later rocks.2 In Germany Siluriaii rocks appear in a few detached areas, but- present a great contrast to those of Bohemia in their coniparativcly unl'ossiliferoiis character, and the absence of any one continuous succession of the whole Siluri.n system. They occur in the Thuringcr Wald, where a series of fucoidal-schists (perhaps Cain- bi-ian) passes up into slates, grcywackes, &e., with Li'n_(/ula, Disciim, Cul_I/mcnc, numerous graptolites, and other fossils. These strata (from 1600 to 2000 feet thick) may represent the Lower Silurian fOl'lll3.tl01]S. They are covered by some graptolitie aluii1- slates, shalcs, flinty slates, and liinestoiies (Faz'0sz'tcs G'othIamlica, &e.), which no (lo1ibt represent the Upper Silurian, and pass into the base of the Devonian formations. Among the llarz Moiiiitaiiis certain greywaekes and shalcs containing laiid—pl-ants (lycopods, &e.), trilobites (D¢LIu1anz'tc.9, &c.), graptolites, &c., are regardc-1 as of intermediate age between true Upper Silurian and LowcrDevon- iaii rocks. In the nortli—west of Fraiice an iinpovcrished series of sandstones and slates represents the succession of forinations up to the top of the Silurian or base of the Devonian system, and contains I a suite of trilobites which indicate more analogy with the Silurian fauna of Bohemia and of Spain than with that of the British Islands. In the western half of the Spanish peninsula Silurian rocks are found ﬂanking the older schists and crystalline masses, and spread- ing over a vast area of the tablclaiid. They appear to belong chieﬂy if not wholly to the lower division of the. system, and they I include reprcseiitatives of I}arrandc’s primordial zone, containing 19 species of orgaiiisins, of which 9 are primordial trilobites. NORTH A)IEltIC..—Ill the United States and Canada the Silurian formations spread continuously over a vast territory, from the mouth of the St Lawrence south- westwards into Alabama and westwards by the great lakes. They almost encircle and certainly underlie all the later Palzeozoic deposits of the great interior basin. The rocks are most typically developed in the state of New York, where they have been arranged as in the sub- joined table. J}. ('12);-or ,S'ilm'z'an. 7 .'-. - H1’, I Oi-iskany sandstone (.S'pi2-ifc-r arcnosus). r (4) Upper Pentamerus limestone (Penta- mcrus pscud0_r]alcatus) . . .. (3) Delthyris limestone (J[cri'.9tcll(r I(c7:z's) (2) Lower Peiitaniems limestone (Penta- mrrus galcatils) ....................... .. (1) 'atei'-lime ('1'entaculitcs, L'iu'_I/- ]7f1'I'll.‘.‘, and I ’tcr_I/__r/otus) ............. .. Onend;1_~_;o salt group, nearly barren of fossils ...................................... .. { (3) Niaga1':i shale and limestone (I[aIy- sins‘, Farosﬂcs, Cal;/nmic Blmncn- bacIu'z', Ilonzalmzolus clcIpI¢z'nocc- Mull us, Lqitrcna tran'L'cr.9ali'.9, 8:0.) (2) Clinton group (I’c11tm)ir7-us oblongus, A/2'3/pa 7'cticula1'i's, &e.) ............. .. (1) Medina group with Oneida eon- _ gloinerate (.l[o(ZioIopsi's orthonota) I 11. Lower I Ielderberg -l Forination. Ludlow. II. Salina F oriiiation. Yenloek. __,,.._.J__...jw_.__. I. Niagara I‘ oi-niation. L-IIIICI. Llan- d overy. an 1 SI)/st. Silmx, vol. ii. suppt., 3. ‘.260, 1877. 9 Barrande, SI!/st. Si'lzIr., vol. i. s11ppt., “ '1'i'i1obites," 1371.