Geology and Mineralogy. 253 



3. The Triassic Cephalopod Genera of America ; by Alpheus 

 Hyatt and James Perrin Smith. Prof. Papers, No. 40, IT. S. 

 Geol. Su'rv.j 1905, 214 pp., 85 pis. — This extensive monograph of 

 marine Triassic cephalopod genera is practically the work of the 

 junior author, ''but the inspiration and general supervision of 

 the work was [the late] Professor Hyatt's contribution." "In 

 this work every genus of cephalopods known to occur in Ameri- 

 can Triassic strata is described, and a representative species under 

 each one is described and figured." 



The marine Triassic development of Idaho, Nevada, Oregon, 

 and California is unusually complete. The lower (800'), middle 

 (1000'), and upper (2000') members "are represented by calcare- 

 ous deposits, aggregating approximately 4,000 feet in thickness." 

 In addition to a summary statement of the various sections and 

 their cephalopod species, this work defines in detail 85 genera 

 (20 new) and 88 species (66 new). For many of the species the 

 stages of growth are also described. Of the genera, 80 are Am- 

 monoidea, 1 belongs to the Belemnoidea, and 4 are Nautiloidea. 

 Of the ammonoid genera, 22 are restricted to western North 

 America ; the rest are also found either in Europe or Asia. 

 Fifteen are common to America and Asia, 10 to Europe and 

 America, and 33 to the three regions. Of species, 7 ammonoids 

 and 1 nautiloid are common to the Alps and America. 



From these statements, it is seen that the ammonoids are very 

 widely distributed, and as early as Triassic time are, as is well 

 known, likewise excellent horizon markers, not only for closely 

 adjoining regions, but also for inter-continental correlations. 



This work is of great value, not only to the student of the 

 Ammonoidea, but as well to the stratigrapher of Triassic forma- 

 tions, c. s. 



4. Miocene Foraminifera from the Monterey Shale of Cali- 

 fornia ; by Rufus M. Bagg, Jr. Bull. No. 268, U. S. Geol. 

 Surv., 1905, 55 pp., 11 pis. — The Monterey shale is from 2000 to 

 2500 feet thick. The bulk is made up of diatom skeletons, but 

 there is also present an abundance of well-preserved Foraminifera. 

 The clay maii of Graves Creek, San Luis Obispo County, has 

 yielded a fauna of 66 species in 17 genera. There are no arena- 

 ceous genera, warm-water Miliolidge, and but one Nummulite, 

 but a large number of rotaline types are present. This faunal 

 composition, the author states, " shows the purity of the waters 

 in oceanic circulation," and less than 500 fathoms deep. Most of 

 the species are those of living forms. The illustrations are excel- 

 lent, c. s. 



5. North Carolina Geological Survey. Vol. I, Corundum 

 and the Peridotites ; by J. II. Pratt and J. V. Lewis. 8°, pp. 

 464, pi. xlv, figs. 35. Raleigh, 1905. — This volume presents very 

 fully the geology, petrology and mineralogy of the belt of corun- 

 dum-bearing rocks of western North Carolina. The peridotites 

 and associated basic magnesian rocks are first taken up and the 



Am. Jour. Sci. — Fourth Series, Vol. XX, No. 123. — March, 1906. 

 18 



