60 Js he American Geol Og ist. January, 1892" 
that the typical Carboniferous section is found. (p. 81.) The limits of 
the system here are well defined both above and below, but in other 
places it shades off into the Devonian below or the Permian above. In 
these cases an arbitrary line must be drawn to indicate the limits of each.. 
Again in the discussion of the Lower Carboniferous strata of the 
Mississippi valley, it is proposed to use the term Mississippian series in 
place of the old name Subcarboniferous, upon the ground that the old 
name is inappropriate, and was ‘introduced as an expression of confus- 
ion and dissatisfaction with the correlations attempted.” (p. 142.) This 
is a slight modification of the late Dr. Winchell’s term Mississippi, ap- 
plied by himto the same series of strata. American geologists have 
not hitherto fallen in with the recommendation, and they may be slow 
to follow Prof. Williams in both of these proposed changes. The 
scheme proposed for the Subcarboniferous rocks of the Mississippi 
valley is as follows: 
ee { Chester. 
Genevieve Group..~ St. Louis. 
| Warsaw (in part). 
MISSISSIPPIAN 
t Series. | Osage Group....... 
| Subcarboniferous. | } 
) Keokuk. 
| Burlington. 
j Chouteau lime-stone and the **Verm- 
Chouteau Group...- icular” and “Lithographic” formations 
| ( of Broadhead. 
In the chapter on the Permian problem the conclusion is reached that 
as far as the strata of Kansas and Nebraska are concerned there is no 
Permian system, the passage from the Coal Measures being gradual and 
not abrupt. The application of the term is here considered purely artific- 
ial, and induced by those who sought to force a correlation between the 
rocks of Europe and America. As for the Permian ranking asa separate 
system he says it is still an open question, “and bids fair to continue so: 
until a natural method of classification for the time-scale be devised, 
which shall be independent of the lithologic character of the rocks.” (p. 
209.) 
The general remarks and conclusions are well worthy of careful pe- 
rusal. That to paleontology is given the first place in all correlations is. 
evident throughout the work. We have already shown his opinion of 
the theory of “persistent parallelism of strata” and it is reiterated on page 
263. Here, also, he refers to the value of fossils, correlations by their 
aid being based upon actual evidence, which can be corrected by a criti- 
cal review; while the particular form of any organic structure is consid- 
ered determined by heredity and environment. “Hence we may deduce 
the law that, given the locality and the conditions of environment, the 
fossil has in itself the evidence of its geologic age.” (p. 263.) In the 
Mississippian province he advocates a structural and a time scale of for- 
mations. From the first point of view there should be an increase in the 
number of formations; while from the paleontological standpoint the 
classification is too minute and the number of formation should be re- 
duced. 
A new feature is introduced in the consideration of geographical 
features as modifying geological classification, but it is not elaborated to 
=—— oa 
