50 
CORRESPONDENCE. 
An elaborate table (of 110 quarto pages) enumerates all the micro- 
scopic objects determined from these many gatherings, according to 
the above-named zones, and the respective depths, from 100 to 
20,000 feet ; materials from less than 100 feet are not included, being 
possibly of land or fresh-water origin, and therefore not indicative of 
real marine conditions. 
These are — Foraminifera ( Polythalamia ) 605, Diatomaeem ( Poly - 
gastrica) 656, Polycystina 279, Phytolitharia (Pooliths and Spongo- 
liths) 219, Geolitliia 56, Zoolitharia 39, remains of Molluscs and other 
animals 70, soft Plant remains 21, inorganic particles, crystals, and 
Morpholites 35. References to the descriptions and figures in the 
author’s various memoirs are also given. His latest corrections and 
arrangement of the minute oceanic organisms, (1.) independent Pro- 
tozoa and Diatomacece (1540), with higher Invertebrates (70), and 
(2.) not independent organisms, but fragments and particles, named 
for convenience of recognition (314), are incorporated in the Table. 
The nomenclature is that which Ehrenberg has adopted through- 
out his long-continued studies of the Microphytes and Microzoa, 
and may readily be correlated with that adopted in the critical 
treatment of his other works by modern naturalists, as in ‘ Annals 
Nat. Hist.,’ Ser. 4, vols. ix. and x. The contents of one of the 
twelve beautiful plates of this memoir in the ‘ Abhandlungen kou. 
Akad. Wiss. Berlin ’ fiir 1872, namely, pi. i., with part of pi. ii., 
illustrating the Foraminifera of Davis Strait, from 6000 to 10,988 feet 
of depth, has been thus brought into relation with the modern nomen- 
clature in the ‘Manual and Instructions for the Arctic Expedition,’ 
1875, p. 194 ; and tbe figures of Foraminifera * from the East Coast 
of Greenland, published in ‘ Die zweite deutsche Nordpolarfahrt,’ &c., 
vol. ii., 1874, Zool. 15, Polythal., pi. i., are similarly treated in this 
‘Arctic Manual,’ at p. 571. The Arctic Rhizopods are thus shown to 
be comparable with those already described by others from the Arctic 
and North- Atlantic oceans, and their local differences of facies can be 
satisfactorily valued. In like manner, all deep-sea explorations will 
have to be studied with reference to what Ehrenberg has already 
done. 
Another great work — on the fossil earths and rocks, marine and 
fresh-water, of all lands, and particularly the Polycystina-bed of Bar- 
badoes — was brought out by the indefatigable Ehrenberg in 1875. 
This volume f comprises, first, a resume of the marine microscopic 
fossils treated of in the ‘ Monatsbericbte ’ and ‘Abhandlungen’ of 
the Berlin Academy, and in the ‘ Mikrogeologie ’ (1854). This is an 
elaborate table (of 98 pages), arranged in geological order — thus, 
I. Primary ; II. Jurassic : III. Chalk ; IV. Tertiary ; Y. Quaternary 
and Recent ; VI. Volcanic : also geographically for Asia, Africa, 
* Drawn by Clara Ehrenberg with the truthful skill of the father’s pencil. 
f ‘ Fortsetzunjr der mikrogeologischen Studien als Gesammt-Uebersicht der 
mikroskopischen Palaontologie gleiehartig analysirter Gebirgsarten der Erde, mit 
speeieller Riicksieht auf den Polycystinen-Mergel von Barbados, von Cliristian 
Gottfried Ehrenberg.’ Aus den Abhandlungen der Konigl. Akad. der Wissen. 
zu Berlin, 1875. Mit xxx Tafeln. 4to, 1875, Berlin. Bead before the Academy, 
December 17, 1874. 
