268 Review of Recent Geological Literature. 
problems of general interest and importance, such as the mi- 
gration of animals and plants and the permanency of the ocean- 
basins but at some future time we may return to these topics 
and consider them as their importance deserves. 
REVIEW OF RECENT GEOLOGICAL LITERATURE. 
BracJf,iospongidse: A memoir on a group of Silurian sponges; with six 
plates. By Chas. Emerson Beecher. (From the memoirs of the Peabody 
Museum, of Yale University, vol. ii, part 1, New Haven). Into this 
valuable paper are gathered and grouped systematically all important 
information concerning the rare class of fossils which, while first dis- 
covered by Dr. G. Troost, in 1838, and partially elaborated by Von 
Zittel and Dr. G. J. Hinde, and classified by Dr. F. E. Schulze, have 
now been first referred to their stratigraphic place. Troost described 
and figured the fossil without giving it any name, stating that it was 
obtained in Davidson county, Tenn. After some changes of owner- 
ship, and with some doubt thrown on its identity with the original 
specimen, it was placed in the hands of Prof. 0. C. Marsh who de- 
scribed and named it Brachiospongia vcemerana, in 1867. Another 
species was named hy him B. lyoni. 
In 1858 Dr. D. D. Owen had referred them to Scyphia Oken, and in 1862 
Prof. R. Owen inadvertently altered this to Syphonia. To Prof. Marsh 
therefore is due the credit of separating it from other genera and the 
erection of the new genus BracJdospongia. This genus has since been 
recognized by Le Conte, Miller (S. A.), Zittel, Roemer and Hinde. 
Recent careful examinations in Kentucky have led to the discovery 
of the exact stratigraphic position of this curious and rare fossil. Hav- 
ing been found only as isolated fossils in loose fragments of limestone 
they could only be referred in general to about the middle of the Si- 
lurian. Mr. E. C. Went, of Frankfort, Ky., has, however, found it in 
place in a " fine cherty, nodular limestone, above the horizon of 
Orthis horealis, which has been considered as the upper member of the 
Trenton." This horizon has been traced over a considerable extent of 
territory. But a single specimen (of B. digitata) has been found from 
any other horizon, viz., the middle Hudson, at a somewhat higher 
horizon. 
On the ophiolite of Thurman, Warren County, N. Y., with remarks on 
the Eozoon canadense. By Geo. P. Merrill. (From the Am. Jour. Sci. 
Mar., 1889). In this paper Mr. Merrill agrees with most, if not all, 
lithologists who have examined microscopically the rock contain- 
ing the form that has the name of Eozoon canadense, and refers it, 
though with due caution owing to the lack of material and of suflicient 
field-examination, to a metasomatic alteration of pyroxenic granules 
to serpentinous matter. "Irregular canals of serpentinous matter cut 
through these aggregates, following cleavage and fracture lines." He 
