REVIEWS 569 
so successfully determined. The lines of differentiation are shown 
already to have deployed in many directions in the earliest Cambrian 
time, and many lines became extinct during the Cambrian. 
In order to show the magnitude of the contributions to our knowl- 
edge of Cambrian brachiopods during the past few years by Dr. 
Walcott, it is only necessary to make comparison with the number of 
forms recorded in earlier works. In Schuchert’s Synopsis of American 
Fossil Brachiopods, published in 1897, 116 species and varieties of Ameri- 
can Cambrian brachiopods are recorded, while in the present work 474 
such forms are described, an increase of over 300 per cent. In the same 
work by Schuchert the following numbers of species and varieties are 
recorded from the remaining Paleozoic systems: Ordovician 319; Silu- 
rian 311; Devonian 663; Carboniferous 478. These numbers would in all 
cases be somewhat augmented were a new brachiopod census taken at 
the present time, but the increase would be in no manner comparable 
with the 300 per cent increase in our known Cambrian forms. Through 
the publication of this work of Dr. Walcott the records of the Cam- 
brian brachiopod life are made more complete than for any other geo- 
logic period. 
S. W. 
The Physiography and Geology of the Coastal Plain Province of 
Virginia. By WrtttamM BUuLLock CLARK and BENJAMIN 
LERoy MILLER. With chapters on ‘The Lower Cretaceous,” 
by Epwarp W. Berry; and “‘The Economic Geology,” by 
THoMAS LEONARD Watson. Bull. IV, Virg. Geol. Survey. 
Pps 74-]pisei9; ©. map. 
A valuable and detailed contribution to the physiography and 
geology of the Coastal Plain. The formations are minutely described 
and well illustrated; tables are given containing complete lists of 
the fossils found together with their geographic and_ stratigraphic 
distribution. 
The submerged portion of the Coastal Plain is comparatively smooth 
near the edge of the continental shelf, but nearer land there are numerous 
small hills with their long diameters roughly parallel to the shore line. 
The submarine covering near shore consists of fine sands mixed with 
broken molluscan shells, and local deposits of pebbles and blue mud; 
farther from shore finer deposits are found. The emerged portion of the 
plain slopes with gradually decreasing gradient to the shore line. Topo- 
