Page:EB1911 - Volume 27.djvu/275

Rh Turtles became well established during this period (Psammochelys, Chelyzoon). Of great interest is the discovery of the earliest traces of mammals in the Trias of Europe, South Africa and North America. The imperfect remains (teeth and jaw-bones) do not admit of any certainty in deciphering their relationships. Microlestes from the Rhaetic of England and Württemberg and Dromatherium from North America are perhaps the best known; Tritylodon from South Africa may also be added. Among the lower forms of marine life foraminifera and sponges play a subordinate part. Corals, which with the calcareous algae built considerable reefs in some regions, at this time began to assume a modern aspect, and henceforth the Hexacorallids took the place of the Palaeozoic Tetracorallid forms (Stylophyllum, Pinacophyllum, Thecosmilial. Crinoids were locally very numerous individually (Encrlnus lilizformis, Dadocrinus gracilis). Urchins were not very common, but an important change from the Palaeozoic to the Mesozoic type of shell took place about thisftime. Brachiopods were important; rostrate forms like Terebratula and Rhynohonella from this time onward became more prevalent than broad hinged genera. Pelecypods were abundant, Myophoria, Halobia, Daonella, Pseudomonolis, Avicula, Gervillia and many others." Gasteropods also were numerous; at the beginning of the period, as in other groups, many Palaeozoic forms lingered on, but one of the main changes about this time was the development and expansion of siphonostomous forms with canaliculate shells. Quite the most important Mollusca were the Cephalopods. In the early Trias there still remained a few of the Palaeozoic genera, Orthoceras, Hungariles, and forms which linked up the goniatites with the ammonites, which henceforth took the lead in numbers and variety. Prionolobus, Aspidites, Celliles, Meekoceras, Tiroliles, Plychites, Tropiles, Ceraliles, Arcesles, Psiloceras and Flemingiles are a few of the prominent Triassic enera. The nautiloids were fairly well represented, but they exhibit no such marked development from Palaeozoic to Mesozoic types as is shown among the ammonoids. In the tabulated synopsis of the Triassic system given below it has been impossible to include many of the names of groups and subordinate divisions. Some of these, such as the term “ Noric ” (Norian), have been used in a variety of ways. A clear account of the history of the study of the Trias will be found in K. A. von Zitteys History of Geology and Palaeontology (Eng. trans., London 1901.

REFERENCES.-The literature of the Trias is very voluminous. A full account, with full references as to date of publication, in Lellzaea Geognostica, ed. by F. Frech, Theil II.; Das Mesozoicum, Bd. i. “ Einleitung des Mesozoicum und der Trias" (F. Frech); “Continentale Trias” (E, Philippi and ]. Wysogorski), 1903; 2nd Lieferung, “Die asiatische Trias ” (F. Noetlingly 1905; 3rd Lieferung, “Die Alpine Trias des Mediterran-Gebietes ” (G. von Hathaber), Stuttgart, 1905. (J. A. H.)

TRIAZINES, in organic chemistry, a series of cyclic corn pounds, containing a ring system composed of three carbon and three nitrogen atoms. Three series are possible, the positions of

CONTINENTAL TRIAS. MARINE TRIAS or THE ALPINE AND INDIAN TYPES. G. . . . . . Alpine Zone. .

erman Trias. England. North Alpine Region. bouth Alpine Region. Fossils India. America. Rhaetic or Ma alodgn

S a n d Stones PQ na rt h .gg Kossen Rhaetic Kossen limestone 2 and Clays beds 'C U -9 beds Dashstem beds and “ Hoch- Star Peak ES with /lvicula White Lias, E75 'Q Lithoden- Kalk and (Azzarola 14111614111 gcbergskalk " beds 2 contorta black pa- < Q EE dron Kalk Dolomite beds) 6011¢07'l¢l in part LZ per-shales, E =.

fl'13flS *ii 3 Aulacothyris Sandstones

Bone bed B one b eCL Q g        limestone with dino-Swbensand- Red a “d £3 #ii fi S“§§§§ "” .?;1$1d2§ d§ {.l 5 Q stein mottls d *cg t' 7;=' ¢ Dachstein § g Dachstein a = marls Wlth 17,3 Q Q Kalk and -5 -5 Kalk and Turbo Coral mme- .,, § Q 'Oak ' salt  QD '5 Coral 'U 'U Coral (Worthrnia) St(-me .Q Q. an § YP' ~' UV 'DZ limestones E E limestones solilarius  5-5'Schilfsand- Sum, §§ “*~§ -E g;= Halmles 3 »

Stein Varliousléf EE Q ~[-° »<. z beds Q

- . ...  cooure ei-mf. — T' “ ""'  Ois G, -em d0|Om Sandstoneg E5 an. 3. Opponitz Raibl beds Tmmtes Hauerztes D Taylorvillc Q- ite and marls  gg' 11' hmestonff and Subbullalus beds E b@<1S°fC=-3 Lettenkohlen- (with“W{=§ - 3 EE -E d910m1t@ ' S it;  forma = Sarlflsteill f@f's'f0nes) “5 is O 'cg Remgrabner cn Trachyreras d lp - »-Dplomitic Conglomer- /3,75 S. U Lbeds andi 'B 3:    gg aomdes 0 omite Q  iz§ ;..:““ = -2 “';;, f;“' »: webs Dfwm Sandstone. an mar S °'~'3 so -ll- .ti, Q SIQE il- beds with plants, -EE Ea 5 EE .Q 3 3" 'U C - Richmond,

M h 1-'»-.E R    -5 2 63 G E;!'§ : gin Trachyoeras Daonella Virginia Haupt- LISC C - ' "“ E Cl mg 'U in ij: O G3 U0 gon beds balk is is -'§ limestone E Q § S E gas Weflgefl Daonella -D-°=-'E-* — and Part- Q: oi '° O 53 beds lommeli E nach beds    $.13 Bl1Cl'i€¥1' P7,0t7ac]?yCc Anhydrite group, Di H 'V H as stem ras reitzi g dolomite and   3 § 3 lg beds

Ts marls with rock- °2 W: " "“"" "' "f' "". —é salt and gypsum E gg; T) & li Tfmodosss beds Cgmmgs Ptychites Koipato beds -f-1 E 8 5' Q   (Prezzo lime' trinodosus beds 3 <  Mg jg “ Alpine cj, Z 3 stollel ...

§ Zellendolomit ET? U; 2: lVlkui U A O  (, K5

Q2      ';Ef      f Hezlenstro- gn Meekocems l"" I ~.

Upper; division Uppermot- E; 3 Campil beds Campil beds Naiifm "ma beds § beds' Idaho or Roth glidlsand- E,, coslota prinolobm if "1 v. . . "

Middle division Pebble beds  .Q, =§ sets beds sets beds p, ,, ,, ,;, ,, ,, ,, ,, ,, - beds £ 3 Of Haugtsznd' J, ” Q HL',, nd clarai 0, ,, Ce, ,, , = stem an os- - o

ag gesensandstein) ';, '§ gg? (Pet;§ g;n> Lower division Lower mot- 5 -F I U7 »§ 2

sandstones with tled sand- Q § " 'Q

4 Q

occasional oolite stone: III 3

(Rogenstein) ~ ~ D