58 Review of Recent Geological Literature. 
diversely striated, are referable, for the great majority of cases, to deflec- 
tions of the glacial currents near the border of the ice-sheet during its 
recession, belonging thus to a single glacial epoch rather than to succes- 
sive ice-sheets separated by an interglacial epoch. But in some instances, 
notably in northern Indiana, president Chamberlin has observed 
crossing systems of strise that quite certainly belong to different epochs. 
There are also in the same district two sets of moraines, which com- 
plete the demonstration of a movement from the east that over-rode 
territory previously invaded from the north. 
Considering the abrading and scoring action tf the ice-sheet, it is 
compared to a plow, a file, and a sled ; and the author concludes that 
much the larger part of the work of striation and polishing was the 
result of action analogous to that of the file. The simplest form of 
striation, consisting of fine, hair-like lines, is attributed mainly to 
sand and silt caught between the larger erratics and the bed-rock over 
which they were being forced. Where larger, obdurate particles were 
entrapped, deeper scorings were made. Under this view the abrupt 
origin and disappeai-ance of some of the striae are quite readily ac- 
counted for. AVhen a particle was overtaken by a slab or a flat-bot- 
tomed boulder embedded in the ice, it was forced strongly into the 
under surface and kept in action as a graver until the boulder passed 
over it, unless sooner worn out or crushed, when it was abruptly freed 
from the exceptional pressure. 
The manifold phases of glacial planation, embossment, grooving, 
striation and polishing are very fully discussed in this paper, as to 
their characteristics, their mode of origin, and their significance 
respecting the history of the glacial epoch; and the map displays the 
limits of the drift-covered area across the United States, and the 
courses of the glacial striae. 
Die Stdmme des Thierreichs. Von M. Neumayr. Erster Band : 
Wirbellose Thiere, 1889. The first volume of this remarkable work 
has recently appeared. It is a large octavo comprising over GOO pages, 
illustrated by 192 cuts, and is the outcome of more than a quarter of a 
century's work and observation . The first one hundred and fifty pages are 
devoted to the general discussion of animal morphology and evolution. 
The chapters on the various sub-kingdoms are each introduced by a full 
consideration of the leading anatomical features after which is a more 
detailed notice of the sub-groups. The Protozoa occupy approximately 
55 pages ; the Ccelenterata, 140 pages ; Echinodermata, 150 pages, and 
the Vermes 95 pages. The part relating to the echinoderms is partic- 
ularly interesting and suggestive. The obscure and curious group of 
cystids appears to be of considerable more importance than has hither- 
to been commonly regarded. The genetic relations of the Echinoder- 
mata are thus expressed : 
Crinoids. Echinoids. Stellerids. 
-Cvstids. 
