1903.] BROOKS—NEW GENUS HYDROID JELLY-FISHES. Na} 
Jurassic and Cretaceous Formations of the Middle West,” by 
Prof. John B. Hatcher, of Pittsburg. 
“Hints on the Classification of the Arthropoda, the Group 
a Polyphyletic One,” by Prof. Alpheus S. Packard, of Provi- 
dence. 
“Anatomy of the Flosculariidx,” by Prof. Thomas H. 
Montgomery, Jr., of Philadelphia. 
“ A Résumé of the Composition of Petroleum from Differ- 
ent Fields,” by Prof. Charles F. Mabery, of Cleveland. 
ApRIL 4.—Mornine Ssssion, 10 A.M. 
President SMITH in the Chair. 
The following papers were read : 
“The Most Insidious Source of Error in Quantitative 
Chemical Research,” by Prof. Theodore W. Richards, of 
Cambridge, Mass. 
“ A Further Classification of Economies,” by Prof. Lindley 
Miller Keasbey, of Bryn Mawr, Pa. 
“Some Features of the Supernatural as Represented in 
Elizabethan and Jacobean Plays,” by Prof. Felix HE. Schelling, 
of Philadelphia. 
“The Hamites and Semites in the Tenth Chapter of Gene- 
sis,” by Prof. Morris Jastrow, Jr., of Philadelphia. 
“The Warfare Against Tuberculosis,” by Dr. Mazyck P. 
Ravenel, of Philadelphia. 
ON A NEW GENUS OF HYDROID JELLY-FISHES. 
BY WILLIAM KEITH BROOKS. 
(Plate I.) 
(Read April 4, 1902.) 
GENuS DICHOTOMIA. 
Diagnosts of the Genus.—Hydroid jelly-fishes with four radial 
canals which divide dichotomously two, three, four, or more times, 
