542 The American Naturalist. [June, 
scribed two new forms of star-fish. — Mr. Morris read a paper 
on subsidence. December ii, 1888. Dr. McCook read a 
paper on nomenclatures of spiders.— Professor Ryder gave the 
results of his study of Mya arenaria. He also exhibited and 
described a section of the skin of an elephant. Professor 
Leidy spoke of the embryology of Lepas. December 1 8, 1 888. 
Mr. Pilsbry called attention to anomalies in Helix bermu- 
densis.—Dx. Foote spoke of Threnardite.— Mr. Morris read a 
communication on colored glass. — Professor Heilprin summar- 
ized the observations made by the recent Greenland expedi- 
January i, 1889. Dr. Koenig exhibited and described a 
specimen of Anhydrite.— Dr. Leidy discussed the Gregarines. 
January 8, 1889. Professor Ryder made a communication on 
the axial skeleton. 
February 12, 1889. Professor Ryder read a paper on the 
development of the calcified skeleton of Chelonians. Febru- 
ary 19, 1889. Dr. Leidy described some teeth of a fossil 
horse from a limestone quarry in Florida. — Mr. Ives reported 
finding on the omentum of a monkey a number of I'entasto- 
mum. 
March 5, 1889. Dr. Horn referred to the incrustation of 
fragments of wood by the mineral constituents of water or soil. 
—Dr. Leidy exhibited two spiders from Peru, and stated that 
the tooth of a fossil Llama, from Florida, had been received. 
March 12, 1889. Dr. Leidy read a paper on CUona. March 
19, 1889. Dr. Brinton exhibited a specimen of Chrysosple- 
mium americaiium. — Professor Ryder discussed the question 
of mammalian descent.— Dr. Rex exhibited a specimen of an 
undersized trichia from Montana.— Dr. Brewer exhibited 
specimens of yeast and described the development of its cells. 
—Mr. Wingate exhibited and described a new myxomycete.— 
Mr. Ives gave a resume of a paper on " Variation of Color in 
Star-Fish." March 29, 1889. Dr. McCook explained the struc- 
ture of spider webs. 
April 2, 1889. Dr. Koenig described some Kansasite from 
Kansas. — Mr. Woolman called attention to the micro-geology 
of Atlantic City.— Professor Heilprin spoke of the geology of 
Bermuda and the structure of coral reefs.— Professor Ryder 
gave the development of vertebrae in certain lower forms.— A 
communication from Professor Wilson on the production of 
aeratmg organs on the roots of swamp and other plants was 
