Reviews — Clarence King — Survey of Fortieth Parallel. 467 



The high external saddle followed by a lower lateral one. Clyd. 

 modicus, Dtrn., possibly belongs to this genus. 



Choristoceras, Hauer. — Generic type : Chor. Marshi, Hauer, with 

 two-pointed first lateral lobe. Next to it stand several forms with 

 entire-margined, rounded, first lateral lobe. Evolute whorls, free in 

 adult individuals of certain forms, with simple straight ribs, inter- 

 rupted on the convex portion, except in old individuals of certain 

 forms, whose convex portion becomes somewhat flattened or de- 

 pressed. Knobs, disposed in spirals, on the depressed or un- 

 sculptured part of the convex portion. In the whole six lobes, 

 the deeply descending one-pointed anti-siphonal lobe particularly 

 remarkable. Chor. Marshi, Hauer, Chor. Haueri, Moys., Chor. 

 rectangulare, Hauer, and Chor. Buchi (Klipsteinianum, Laube) rank 

 among this genus. 



Melictiies. Mojs. — Whorls evolute, with strong straight ribs, 

 running without interruption over the convex portion. Lobe-line 

 simply undulated, with minute notches, scarcely perceptible by the 

 unaided eye. Species : Mel. genicidatus, Hauer, Hel. Menseli, Opp., 

 Mel. nasturtium, Dtm. 



Badiotites. — The St.-Cassian forms — Ammon. Eryx, Mstr., and 

 Amrnon. glaucus, Mstr., characterized by a narrow or keel-like pointed 

 convex portion, and by falciform ribs, are morphologically so dis- 

 crepant from Choristoceras that they must constitute an independent 

 genus. Lobes entire-margined, undulated ; anti-siphonal lobe long, 

 one-pointed. 



Bhabdoceras, Hauer. 



Cochloceras, Hauer. 



EEVIEWS. 



I. — United States Geological Exploration of the Fortieth 

 Parallel. By Clarence King, U. S. Geologist. Illustrated 

 by 28 Plates and 12 Analytical Geological Maps. (Washington, 

 1878.) 



THIS fine work forms the first volume (although the last pub- 

 lished) of the Eeport of the Geological Exploration of the 

 Fortieth Parallel, under the direction of Clarence King, its subject 

 being the '•' Systematic Geology " of that region. The Exploration 

 has covered a belt of country about 100 miles wide from N. to S., 

 and 800 miles long, extending from the eastern foot of the Eocky 

 Mountains to the Sierra Nevada of California, or almost across the 

 Cordilleras where they are the broadest. Assisted by an ardent and 

 untiring corps (including A. Hague, S. E. Emmons, and others) 

 Mr. King has endeavoured to work out the continuous geology of 

 this almost unexplored gap connecting it, as far as possible, with the 

 territory surveyed by Whitney on the one hand, and with Hayden's 

 field on the other. 



The purpose of this volume is to present a brief systematic account 

 of the data collected, and the inductions deducible therefrom, so that 

 the arrangement is chronological, beginning with the deposits of 



