weeks.] PALEONTOLOGY, PETROLOGY, AND MINERALOGY, 1894. 107 
670 Wright (Albert A.). On the ventral armor of Dinichthys. 
Ohio Geol. Surv., vol. vii, pp. 620-620. 
Reviews some of the previous descriptions of the ventral armor of 
Dinichthys. 
071 The ventral armor of Dinichthys. 
Am. Geol., vol. xiv, pp. 313-320, pi. ix, figs. 1-2. 
Describes material collected from the Cleveland shale of Ohio. 
672 Limits of the glaciated area in New Jersey. 
Geol. Soc. Am., Bull., vol. v, pp. 7-13. 
Abstract: Am. Geol., vol. xii, p. 166 (f p.). 
Describes the character of the glacial material, the topography of 
the region and its influence on glaciation, the determination of the 
limits of the glaciated area, and the duration and efficiency of glacial 
ice. 
673 Wright (G. Frederick). Continuity of the Glacial period. 
Am. Jour. Sci., 3d ser., vol. xlvii, pp. 161-187, flgs. 1-7. 
Abstracts: Am. Geol., vol. xiii, p. 286 (i p.); Am. Nat., vol. xxviii, 
pp. 508-510. 
Discusses the evidences as to whether the erosion of the rocky gorge 
of the Ohio and its tributaries was pre-Glacial or inter-Glacial, illus- 
trated by four maps. Reviews the evidences of pre-Glacial erosion in 
the Delaware valley, and gives a summary of the events of the Glacial 
period. 
674. The Cincinnati ice dam. 
Pop. Sci. Mo., vol. xlv, pp. 184-198. 
Discusses the evidence which indicates the former existence of an ice 
dam in the viciuity of Cincinnati. 
674& [Past drainage systems of the Upper Ohio basin.] 
Abstract : Am. Geol., vol. xiii, p. 219 (A p.). 
674ft Glacial history of western Pennsylvania. 
Abstract: Am. Geol., vol. xiii, pp. 219-220 ($ p.). 
675 Wurtz (Henry). The density of the earth. 
Sci. Am. Suppl., vol. xxxvii, p. 15028. 
Discusses some of the methods used by certain investigators to ascer- 
tain the earth's density. 
676 Gold genesis. 
Sci. Am. Suppl., vol. xxxviii, pp. 15644-15645. 
Reviews the theories as to the origin of gold. 
z. 
677 Zittel (K. von). [Correlation of clastic rocks.] 
Int. Cong. Geol., Gompte Rendu, 5th session, p. 155 (A p.). 
Discusses briefly the relative value of plant and animal remains for 
purposes of correlation. 
