Geology. 511 



by Aug. F. Foerste. Bull. Sci. Lab., Denison Univ., xvii, pp. 

 17-174. pis. i-xviii, 1912. — The greater part of this work is 

 devoted to detailed descriptions of 41 species (9 new) .of brachio- 

 pods and 2 other new fossil forms. Throughout the descriptions 

 and on the introductory pages is presented an immense amount of 

 stratigraphic detail along with the geographic distribution of the 

 species discussed. On page 23 is a revised table of the Cincin- 

 natian and Mohawkian formations embracing no fewer than 50 

 stratigraphic subdivisions. In the last paragraph (page 139) the 

 author makes three generic changes affecting brachiopod genera 

 proposed by him in 1909, but the reasons for the substitutions are 

 not stated. These are Schizoramma for Schizonema, Pionodema 

 for Bathyccelia, and Encuclodema for Cycloccelia. c. s. 



6. The Arnheim formation within the areas traversed by the 

 Cincinnati geanticline ; by Aug. F. Foerste. Ohio Naturalist, 

 xii,No. 3, pp. 429-453, pis. xx-xxii,1912. — The Arnheim formation 

 is in the upper part of the Ordovician and at the base of the Rich- 

 mond series. Its distribution in Kentucky, Indiana, and Ohio is 

 here described. It is in this formation that the Richmond faunas 

 make their appearance, but the source whence this migration 

 came the author does not state, though he seems to favor an 

 entrance from the southwest toward the northeast. The Arnheim 

 is also a time of crustal warping and the breaking down of some 

 unknown barrier, permitting the introduction of the Richmond 

 fauna. c. s. 



7. JPaleontologia Universalis, ser. 3, fasc. 3, July, 1911. — This 

 recently published fasciculus of reproductions and emendations 

 of poorly understood invertebrate species (1821-1850) treats of 

 25 forms recorded on 56 sheets. c. s. 



8. Petrographic Methods. Translated from the German of 

 E. Weinschenk by R. W. Clark. 8°, pp. 396, figs. 371. New 

 York, 1912 (McGraw-Hill Co.). — No more convincing evidence 

 of the fact that petrology has become a definite science, which 

 occupies a field of its own, can be found than in the appearance of 

 volumes devoted to a description and discussion of its technical 

 methods, such as the one before us, and that noticed in the follow- 

 ing review. This work of Professor Weinschenk has now been 

 used for several years in the original, and has met in German- 

 speaking countries with very favorable consideration in the field 

 for which it was designed. It does not aim at the comprehen- 

 sive and mathematical treatment of subjects which characterizes 

 the great work of Rosenbusch and Wtilfing, but seeks in simpler 

 form, and mostly without mathematical discussion, to convey to 

 the student the essential principles which underlie the optical 

 study, investigation, and determination of crystalline substances. 

 This is accomplished by careful and extended explanations and 

 description of apparatus and of the proper methods of its use. 

 The form of presentation of the matter is, therefore, not merely 

 synoptic of a larger work, as is too often the case in manuals 

 which are designedly somewhat elementary in character, but 

 rather full, so far as the field is covered. 



