A. Vaughan, have worked out in great detail the faunal sequence in their Lower Carboniferous or Avonian rocks (Vaughan 1905, 1915; Garwood 1912; Dixon 1911). While opinions differ as to the placement of the division line between the Tournaisien and Viséen, there is general agreement as to the faunal successions throughout the British and Belgian field. The northern part of the British Isles, however, is characterized by an arenaceous or abnormally marine facies and much remains yet to be done on the correlation of the beds that make up the Calciferous and Limestone series of Scotland. The latter facies is rich in the Mollusca as contrasted to the coralbrachiopod faunas of the calcareous or "Mountain limestone" facies.

In comparing the Windsor faunas with the Avonian faunas of England, the affinities are seen to lie with the upper Avonian or Viséen rather than with the lower Avonian or Tournaisien. The presence in the lower Windsor zone of abundant Composita of the "ficoides" form, associated with Productus of the type of cora and corrugato-hemisphericus, is in striking conformity with the faunal assemblage in the middle Viséen (S2) of the Avonian sequence. Of the Mollusca, which dominate the lowest fauna at Windsor, there are species identical with or closely allied to species from the Lower Limestone series of Scotland, or from the Redesdale limestone of Northumberland, both of which are well up in the Viséen. Thus, Sanguinolites parvus n. sp. is probably synonymous with S. striatogranulatus Hinde from the Redesdale; specimens of S. tricostatus identical with Portlock's species from the Redesdale limestone occur at Windsor; Lithodomus lingualiformis n. sp. is very close to L. lingualis Phillips from the Viséen of Castleton; Murchisonia compacta is identical with M. compacta Donald from the Upper Limestone series of Dalry, Scotland.

The upper or Martinia zone at Windsor is characterized by the entrance of a clisiophyllid cup coral belonging to the genus Dibunophyllum, which is an early form of the type of Dibunophyllum aff. 4 Vaughan, as well as by the abundant occurrence of Martinia of the M. glabra form type. Both of these genera are characteristic Viséen genera, and Dibunophyllum especially has been found a good index to the upper Viséen of England. The following species from the upper limestone of Windsor afford additional links on which a correlation of the

Windsor Martinia zone with the lower part of the Dibunophyllum zone is based.

Zaphrentis minas Dawson is distinctly of the type of Z. enniskilleni Edwards & Haime. In England this group ranges from the upper Tournaisien to the upper Dibunophyllum zone, but is especially characteristic of the Viséen.

Lophophyllum avonense n. sp. In Europe, Lophophyllum attains its maximum in strata of upper Viséen age, or in beds immediately succeeding, although it is found sparingly in the upper portion of the Tournaisien.

Tabulipora acadica n. sp. is a dendroid trepostomatous bryozoan that is very abundant near the base of the Kennetcook limestone. It is characterized by the thinness of the peripheral zooecial walls, which nevertheless show a distinct moniliform structure. Tabulipora is essentially a Viséen genus, and T. tenuimuralis Lee from the Eelwell limestone, Lowick (= D2?), agrees with the Windsor species in the tenuity of its walls.

Avonia spinifercardinata n. sp. is very close to Productus longispinus Sowerby.

Chonetes politus, the only Chonetes yet gathered from the Windsor beds, is identical in all respects with McCoy's species from the base of the Lower Limestone series of Scotland.

Spirifer bisulcatiformis n. sp. is indistinguishable from S. bisulcatus var. oystermouthensis Vaughan from D2-D Gower (Dixon 1911). The bisulcatus type of Spirifer occurs rarely in the middle Avonian but has its maximum in the upper Viséen.

Martinia opertacosta n. sp. This species lacks dental plates and has the shell structure of a true Martinia.

Phillipsia howi Billings. This species has been correlated by Vogdes with P. meramecensis Shumard, on the evidence of pygidia only. Several cranidia, however, found by the writer, one of which is still attached in a crushed rolled specimen, determine the Windsor species to belong to the gens of P. eichwaldi Fischer, which occurs in the Lower and Upper Limestones of Scotland and at Bolland, Yorkshire.

Allorisma sulcatiforme n. sp. is perhaps identical with A. sulcatum Fleming from the Redesdale limestone and the Limestone series of Scotland.

Aviculopecten dissimilis Fleming, from the Limestone series of Scotland and from the Four Laws limestone of

Northumberland, occurs in the upper Limestone of Wind

sor.

Correlation with the American Tennesseean.-The dissimilarity of the Windsor faunas to those of like age in the Mississippian basins of America was early noted by Dawson and subsequently confirmed by Schuchert and Beede. Dawson, moreover, clearly perceived their European alliances and attributed their isolation from the western faunas to the existence of an Appalachian mountain barrier. The difficulties of correlating a fauna which is dominantly a molluscan one are well exemplified by the fact that Beede, who described faunas of this age from the Magdalen islands, was impressed with the Devonian or early Mississippian aspect of some of the pelecypods, whilst earlier paleontologists, e. g., Meek and Newberry, emphasized their Permian appearance. In the present correlation, reliance is placed rather on the occurrence of several brachiopods and bryozoans that either hold a limited range in, or make a definite entry into, the Mississippi Valley basin.

In the upper Windsor zone, several species belonging to Martinia, Composita, and Productus present evidence of an age synchronous. with some part of the Chesterian group. Martinia opertacosta n. sp. is a form closely allied to M. contracta (Meek & Worthen). Composita obligata n. sp., common in, and characteristic of, the upper Windsor limestones, is so close to C. subquadrata (Hall), a characteristic Chesterian species, that it may well be specifically identical. Productus (Avonia) multiplexiseptum n. sp. is likewise probably specifically equivalent to P. parvus (Meek & Worthen) from the Ste. Genevieve and Chesterian groups. Thus there is direct evidence of Chesterian affinities. Indirectly, the same conclusion is reached, as the fauna of the upper zone at Windsor correlates with that of a lower Dibunophyllum age in the European time-scale.

The lower fauna at Windsor, while it likewise indicates Chesterian affinities, is seemingly an earlier expression and may be in part equivalent to the Ste. Genevieve. The Compositas, which are extraordinarily abundant in individual representation, belong mainly to two species of European stock, and while the productids of the cora and semireticulatus types are too plastic for correlation purposes, they likewise are closer to the European species. The occurrence in the fauna of a true Diaphragmus is the

most suggestive character, as this genus makes its first appearance in the Ste. Genevieve and the D. montesana Ulrich (1917) is close to the Windsor D. tenuicostiformis Beede. The bryozoans afford additional evidence in their Chesterian affinities. Thus Batostomella exilis (Dawson) and B. cf. abrupta Ulrich are two species, associated in abundance in the Miller limestone, that are almost indistinguishable in their external and internal characters from B. spinulosa and B. abrupta Ulrich. The fenestellid of most common occurrence, Fenestella lyelli Dawson, reveals close analogies with F. elevatipora Ulrich, while Septopora parva n. sp. has the small delicate zooarium of S. delicatula Ulrich associated with a like arrangement of accessory pores on the reverse surface. It is concluded that the Chesterian affinities of this lower Windsor fauna are too strong to assign to it as low a position as the St. Louis, and it is provisionally referred to the Ste. Genevieve.

Climatic correlation. The semi-aridity characteristic of Tennesseean time in Nova Scotia during the deposition of the Cheverie and Windsor formations is in agreement with conditions of semi-aridity in Pennsylvania during Mauch Chunk time and in Michigan during the deposition of the Michigan series.

BIBLIOGRAPHY.

Beede, J. W.-1911.-The Carbonic fauna of the Magdalen islands. New York State Mus., Bull. 149, 156-186.

Dawson, J. W.-1855.-Acadian geology, 1st ed.; 2d ed., 1868; 3d ed., 1878; 4th ed., 1891.

Dixon, E. E. L.-1911.-The Carboniferous succession in Gower (Glamorganshire) with notes on its fauna and conditions of deposition. Quart. Journ. Geol. Soc., London, 67, 477-567, pls.

Garwood, E. S.-1912.-The Lower Carboniferous succession in the northwest of England. Ibid., 78, 449-586, 13 pls.

Hartt, C. F.-1867.-On a sub-division of the Acadian Carboniferous limestone with a description of a section across these rocks at Windsor, Nova Scotia. Can. Nat., new ser., 3, 212-224.

Schuchert, Charles.-1910.-Paleogeography of North America. Bull. Geol. Soc. America, 20, 551.

Ulrich, E. O.-1917.-The formations of the Chester series in western Kentucky and their correlates elsewhere. Kentucky Geol. Surv. and U. S. Geol. Surv. (joint pub.).

Vaughan, Arthur.-1905.-The paleontological sequence in the Carboniferous limestone of the Bristol area. Quart. Journ. Geol. Soc., London,

61, 181-307, 3 pls.

1915. Correlation of Dinantian and Avonian. Ibid., 71, 1-52, 7 pls. White, David.-1901.-Some paleobotanical aspects of the upper Paleozoic in Nova Scotia. Can. Rec. Sci., 8, 273-274.

-

1913.-Excursion in eastern Quebec and the Maritime Provinces: the Horton flora. 12th Internat. Geol. Congress, Guide Book No. 1 (issued by the Geological Survey of Canada), 144-146.

ART. XI.-Relation of Subjacent Igneous Invasion to Regional Metamorphism; by JOSEPH BARRELL. (Continued from page 19)

PART II. METAMORPHIC AND METASOMATIC RELATIONS OF OROGENIC BATHOLITHS.

HEATING AND CRYSTALLIZING EFFECTS OF MAGMAS.

If subjacent magmas are a primary factor for the production of regional metamorphism, they must act through their heat and emanations. Their magmas, on their initial rise in undifferentiated form, appear to possess a heat of not less than 1200° C., but the final crystallization of granite takes place at temperatures below 870° C. and above 575° C. This degree of cooling must occupy a long time, and as the bodies of molten rock are vast, there is sufficient heat passing out to raise the cover rocks to a highly abnormal temperature. The curves of temperature and their relation to time, as based on the laws of conduction, can not give definite information, since the heat transfer into the cover rocks is doubtless largely by gaseous transfer, in advance of conduction.14 Gaseous transfer could, if sufficiently rapid and prolonged, heat the entire cover to that thermal curve dependent upon the adiabatic expansion and reactions of the gases. Differentiation, by which granites are derived as a final stage from antecedent more basic magmas, implies a low viscosity in all of the earlier stages of magmatic rise. It seems probable that there is saturation with gas under pressures of 1000 atmospheres or more, and at temperatures of the initial intrusions. The great portion of the cover can then be heated up to temperatures at which garnet, staurolite, sillimanite, feldspar, muscovite, and hornblende can crystallize. The temperature conditions for anamorphism may be brought comparatively near to the surface. Above this will be a zone of hydrothermal alteration.

CHEMICAL OR METASOMATIC EFFECTS OF EMANATIONS.

The study of metamorphic formations shows that except for the elimination of volatile constituents the bulk 14 [The mechanism of this advance transfer of gaseous solutions has been outlined by C. N. Fenner, Jour. Geology, 22, 594 and 694, 1914.]