1890.] Geology and Paleontology. 955 
graphic plates. Of the twenty-five species of Polyzoa eleven are new. 
The Ostracoda are few, and not in good condition. There are but 
nine species in all, five of which are new. 
The study of the Calciferous formation in the Champlain valley by 
Profs. Brainard and Seeley has brought a series of surprises: 1. The 
thickness of the rocks,—little less 20co feet. 2. The amount of mag- 
nesian limestone. 3. The amount of pure limestone. 4. The abun- 
dance of fossil forms. 5. The almost entire exclusion of the bird’s-eye 
formation from the Vermont rocks. (Bull. Geol. Soc, Am., pp. 501- 
516.) 
In the Proc. U. S. Nat. Mus., Vol. XII., are found descriptions by 
C. D. Walcott of fossils from the Lower Cambrian. Of seven corals, 
two, Archeocyathus dwightii and Ethmophyllum meekit, are new 
species. Of worms and molluscs there are three new genera and thir- 
teen new species. 
In a report on the Natural Gas in Minnesota Prof. N. H. Winchell 
makes the following statement: ‘‘So far as science affords any evi- 
dence in favor of gas below the Trenton limestone in Minnesota, there 
is perhaps one chance in ten that the formation which is known in the 
northern part of the State as Amimike slates and quartzifes, underlies 
the county of Freeborn at a depth of 3000 feet. In case it were found 
at that depth there might be one chance in one hundred that it would 
contain some gas, and one in a thousand that it would afford enough 
for economic purposes." (Bull. No. 5, Geol. and Nat. Hist. Survey, 
Minn.) 
Prof. Edw. Orton states as a law that ** The pressure of Trenton 
limestone gas is due to a salt-water column, measured from about six 
hundred feet above tide to the level of the stratum which yields the 
gas." (Bull. Geol. Soc. Am., Vol. I). 
In view of the fact that the use of the name Hudson River group 
has been attended with more or less uncertainty ever since it was pro- 
mulgated by the geologists of the New York Survey, Mr. C. D. Wal- 
cott proposes to use the term Hudson in a generic sense to include a 
group of formations that occur between the Trenton limestone horizon 
and the Upper Silurian or Niagara horizon. (Bull. Geol. Soc. Am., 
Vol. L, pp. 335-356.) 
Carbonic.—C. R. Keyes, in discussing variation of a carbonic gas- 
tropod, Platycerus equilaterum (Am. Geol., "June, 1889), emphasizes 
the fact that accidental station is not the only factor in modifying the 
form of the shell, but that gravitation also exerts a potent influence. 
