about

tendency toward the allotriomorphic structure.
Further west,
in the center of the mass, the syenite changes to a darker gray rock
with a tinge of green, somewhat resembling a diorite. It is more
coarsely crystalline than is the syenite and is much more basic. The
minerals are the same as in the syenite, except that quartz is lacking,
but differ somewhat in their character and in the proportions present
in the two rocks. The augite is now a bright green idiomorphic min-
eral. Hornblende is rare and biotite abundant. The great difference
between this rock, which the authors call yogoite, and the syenite, is in
the relative proportions of augite and orthoclase present in them. In
the yogoite the pyroxene predominates over the orthoclase, while in
the syenite the reverse ratio exists. In the western portion of the rock
mass, the prevailing type is shonkinite, a very dark basic rock, very
similar to that of Square Butte. Augite and biotite are very abun-
dant as compared with the orthoclase, which in turn predominates over
plagioclase. This latter mineral is represented by andesine, a more
basic feldspar than that in either the syenite or the yogoite. Analyses
of the three types of Yogo Peak rocks follow:

SiO2 TiO2 Al03 Cr03 FeO3 FeO MnO MgO Cao Bao Sro NaO KO HO Pg05
Syenite 61.65 .56 15.07 tr
2.03 2.25 .09 3.67 4.61 .27 .10
Yogoite 54.42 .80 14.28 tr 3.32 4.13 .10 6.12 7.72 .32 .13
Shonkinite 48.98 1.44 12.29 tr 2.88 5.77 .08
Shonkinite contains in addition .22 per cent. of Fl.

Tota

100.

100.

- 99.

4.35 4.50 .67 .33 3.44 4.22 .60 .59 9.19 9.65 .43 .08 2.22 4.96 .82 .98

From a consideration of the nature of the three types of rock the
authors conclude that the Yogo Peak stock exhibits the results of a
progressive differentiation along its major axis. There is a progressive
increase in the ferro-magnesian constituents from the east to the west
and a consequent increase in basicity. All the components of the three
types exhibit the effects of this differentiation in the proportions pres-
ent in the different rocks. The Yogo Peak mass is thus an illustration
of a "Facies suit" as distinguished from a "rock series." In the for-
mer differentiation took place in situ, whereas in a 'rock series' differ-
entiation occurred before the eruption of rocks into their existing posi-
tions. The facies suit of Yogo Peak together with the rocks of
neighboring mountains comprise a distinct rock series.

The authors close their paper with an appeal for a more specific
nomenclature in petrography-a nomenclature that will take account
not only of the qualitative relations between the minerals that make up
rock masses but of the quantitative relations as well. The Yogo Peak
3 s Compare AMERICAN NATURALIST, 1895, p. 737.

=

=

rocks form a natural series with sanidinite and peridotites. Rocks composed of orthoclase and no augite sanidinite; when orthoclase exceeds augite = augite-syenite; when orthoclase equals augite yogoite; when augite exceeds orthoclase = shonkinite; when augite alone is present = pyroxenite and peridotite. In this scheme the term augite includes also other ferro-magnesian minerals, and the terms orthoclase other feldspars.

In connection with the article above referred to Iddings' mentions the existence of a series of rocks associated with typical basalts and andesites in the Yellowstone National Park. They represent like phases of differentiation belonging to separate, but similar rock families. Most all of these rocks are basaltic looking. They occur in flows and dykes and sometimes as breccias, constituting the major portion of the Absaroka Range. These rocks present a wide range of composition within definite limits, forming a series connected by gradual transitions. Three classes are distinguished, the first of which is characterized usually by abundant phenocrysts of olivine and augite and an absence of feldspar phenocrysts; the second class is characterized by the presence of labradorite phenocrysts in addition to those of olivine and augite, and the third class by the presence of labradorite phenocrysts. The names given to the three classes are absarokite, shoshonite and banakite. The distinctions between the classes is based principally upon their chemical relationships. A large number of analyses, most of which were taken from other papers, illustrate their points of difference. A comparison of the analyses, besides showing the close relationships existing between the rocks of the three classes, shows also what mineralogical differences may obtain for rocks of the same chemical composition. The shoshonite from the base of Bison Peak and the banakite from Ishawooa Canyon have practically the same chemical composition. The former, however, contains abundant phenocrysts of labradorite, augite and olivine, while the latter contains numerous labradorite phenocrysts, but few and small ones of the other two minerals. The groundmass of the first shows much less orthoclase than that of the second, and no biotite, which abounds in the second. The author compares the series of rocks studied by him with the series studied by Merrill, with the series discussed by Weed and Pirsson and with Brögger's giorudite-tinguaite series. The conclusion reached by this comparison is to the effect that it may be doubted whether the gen

'Journal of Geology, Vol. III, p. 935

5 Cf. AMERICAN NATURALIST, 1896, p. 128. 6 Cf. AMERICAN NATURALIST, 1895, p. 567.

etic relations between igneous rocks can properly mark the lines along which a systematic classification of them may be established.

Petrographical Notes.-In a phyllite-schist found in blocks on the south shore of Lake Michigamme in Michigan, Hobbs' has discovered large crystals of a chloritoid like that described by Lane, Keller and Sharpless in 1891. The rock in which the crystals occur is a mass of colorless mica scales through which are distributed large flakes of biotite, small blades of chloritoid, a few acicular crystals of tourmaline and grains of magnetite. Most of the chloritoid is in large porphyritic crystals imbedded in this matrix. The optical properties of the mineral correspond to those of masonite.

In a summary of the results of this work in the upper Odenwald Chelius announces the existence there of two granites-the younger a fine grained aplitic variety and the older a coarse grained porphyritic variety, with a parallel structure due to flowage. Pegmatitic veins that cut this granite are looked upon as linear accumulations of porphyritic feldspar crystals. Many notes are also given on the diorites, gabbros and basalts of the Odenwald, on the basic enclosures in the granite, which the author regards as altered fragments of foreign basic rocks, but nothing of a startling nature with reference to these subjects is recorded. A gabbro porphyry was found occurring as a dyke mass. It consists of phenocrysts of labradorite in a gabbro-aplitic ground.

mass.

In a general paper on the divisibility of the Laurentian in the Morin area N. W. of Montreal, Canada, Adams describes the characteristics of the members of the Grenville series of gneisses, quartzites and limestones. The augen gneisses, the thinly foliated gneisses and the granulites of the series are all cataclastic or granulitic in structure. They are regarded as squeezed igneous rocks. The crystalline limestones and quartzites are recrystallized rocks that are thought to be changed sedimentaries. Pyroxene gneisses, pyroxene granulites and other allied rocks are of doubtful origin. In addition to all these rocks there is present in the series a group of peculiar banded garnetiferous gneisses which from their chemical composition are regarded as in all probability metamorphosed sedimentary rocks.

Amer. Jour. Sci., Vol. L, 1895, p. 125. 8 Amer. Jour. Sci., Vol. L, 1895, p. 58.

GEOLOGY AND PALEONTOLOGY.

The Paleozoic Reptilian Order Cotylosauria.-A paper was read before the American Philosophical Society, November 15, 1895,1 by Prof. E. D. Cope, on the reptilian order Cotylosauria. The following is an abstract of the characters of the order.

Quadrate bone united by suture with the adjacent elements. Temporal fossa overroofed by the following elements: Postfrontal, postorbital, jugal, supramastoid, supratemporal, quadratojugal. Tabular bone present. Vertebræ amphicoelous; ribs one headed. Episternum present. Pelvis without obturator foramen.

This order is of great importance to the phylogeny of the amniote Vertebrata. The structure of the temporal roof is essentially that of the Stegocephalous Batrachia, while the various postorbital bars of the amniote Vertebrata are explained by reference to the same part of its structure.

The palatal elements in this order are more or less in contact on the middle line, and the pterygoids diverge abruptly from this point, and return to the quadrate. The occipital condyle is single, and does not include exoccipital elements (unknown in Elginia).

Intercentra are present in Pariasauridæ, Diadectida and Pariotichidæ, and they are wanting in Elginiidæ. The hyposphen-hypanterum articulation is present in the Diadectidæ, but is wanting in the Elginiidae and Pariasauridae.

The scapular arch is best known in Pariotichida, Pariasauridae and Diadectidæ. In the two former there is a T-shaped episternum, over which are applied the median extremities of the clavicles; and there are well-developed coracoid and praecoracoid. In Diadectidae (probably genus Empedias) the episternum is articulated by suture with the clavicles.

In the Proceedings of the American Philosophical Society, 1892, p. 279, in a paper on "The Phylogeny of the Vertebrata," I wrote as follows: "Moreover, the Pely cosauria and the Procolophonina have the interclavicle, which is an element of membranous origin, while in the Prototheria we have the corresponding cartilage bone, the episternum. This element is present in the Permian order of the Cotylo

1 See Proceedings Amer. Philos. Soc., Vol. XXXIV, 1896, p. 436.

2 Seeley, Philos. Trans. Roy. Soc. London, 1888, p. 89; 1892, p. 334.

sauria which is nearly related to the Pelycosauria." The examination of the sternal region in Pariotichus has led me to the conclusion that the episternum and interclavicle are present and fused together in that genus, and also to the belief that the episternum is present in the genus Procolophon. The structure is generally similar in the two genera, and I think that Seeley is in error in determining the element in question in Procolophon as the interclavicle only. Gegenbaur pointed out in his Comparative Anatomy the different (i. e., membranous) origin of the interclavicle of the Lacertilia, but he included it with the episternum under the same name. The true episternum is not present in the Lacertilia. It is present in the Sauropterygia and Testudinata and probably in all the orders with one postorbital bar, or Synaptosauria, while it is wanting in most or all of the Archosaurian series, and in the Squamata. Whether the element I have referred to in the genus Naosaurus as interclavicle, is that element or the episternum, must remain uncertain until I can see it in place. Its edges are thin, as in the interclavicle of the Lacertilia. Of course, the Reptilian order which is in the line of ancestry in the Mammalian will have an episternum and not an interclavicle only. The Stegocephalia among Batrachia possess an episternum, with, perhaps, an adherent interclavicular layer as in the Testudinata.

Seeley describes four sacral vertebræ in Pariasaurus. In Empedias there are but two. The pelvis is without obturator foramen. The humerus has an entepicondylar foramen. The tarsal and carpal elements are incompletely known.

There are palatine teeth in Empedias and Pariasaurus, but none in Elginia; vomerine teeth none.

The inferior surface of the cranium is known in Elginia, Pariasaurus, Empedias and Pariotichus, and has been described as to the first three genera by Newton, Seeley, and myself. Pariotichus displays generally similar characters. There is a pair of posterior nares, and a pair of zygomatic foramina, but no palatine foramen. The palatine elements meet on the middle line, but gape behind. The vomers (prepalatines) are distinct, and are well developed anterior to the palatines. The ectopterygoid is large and has a prominent posterior border. I have stated that in Empedias there are teeth on the vomer. Better preserved specimens of Pariotichus show that the teeth are really borne on the edges of the palatines, which are appressed on the median line in the former genus. Similar palatine teeth are present in Pariasaurus, but are wanting in Elginia. Teeth are also present on the posterior Philos. Transac. Royal Society, 1889, p. 275, Pl. IX, fig. 9.