abstracts: paleontology 501 



theory is not correct, but some further experiments were necessary 

 to answer Jaeger and von Steinwehr's contention. 



The • authors have analyzed all of their former observations with 

 reference to the volume of the electrolyte, the weight of the deposit, 

 and the purity of the solution. They have also made some further 

 experiments with especially impure solutions and with other forms 

 of the voltameter than the porous cup form. Allof these observations 

 have been treated by statistical methods, and the authors show, first, 

 that the volume effect is not confined to the porous cup form of volta- 

 meter, but that it is common to all forms of voltameter, and, sec nd, 

 that it is caused by impurities in the electrolyte. The authors give 

 a theory of the mechanism of the effect, and they believe that the 

 evidence proves conclusively that the effect is a valuable criterion 

 for the purity of the silver nitrate. G. W. V. 



PALEONTOLOGY. — Cambrian trilobites. Charles D. Walcott. 

 Smithsonian Misc. Coll., 64: No. 3, 1916. 



The purpose of this paper is to afford data to aid in clearing up some 

 of the problems of formations of the Appalachian region by a careful 

 comparison of portions of their contained faunas with those of the 

 Mississippi Valley, the Cordilleras, and other localities. No thorough 

 study and comparison of many genera of the Cambrian faunas has 

 been made, though collections from many outcrops have been in the 

 writer's possession for years, awaiting the opportunity to make these 

 studies so necessary in his work on the Cambrian trilobites. 



The paper is illustrated with fifteen plates, containing 280 figures of 

 trilobites. Two new families are proposed, Menomonidae and Nor- 

 woodidae, and seven new genera: Menomonia, Millardia, Dresbachia, 

 Norwoodia, Saratogia, Vanuxemella, and Hanburia; 46 new species 

 |ind three new varieties are described and figured, with 19 earlier 

 described species and several genera. One of the marked features of 

 the paper is the description of a number of genera of the order Proparia : 

 Menomonia, Millardia, Dresbachia, and Norwoodia. These, the writer 

 says, taken in connection with the genus Burlingia, described in a 

 previous paper [Cambrian trilobites. Smithsonian Misc. Coll., 53: No. 

 2, p. 14. 1908.] establish the existence of a strong group of the order in 

 Cambrian time. 



The stratigraphic position of the Weeks formation is changed from 

 Middle to Upper Cambrian, and the problem of whether the Conasauga 



