REVIEWS. 243 
individual variation. Mr. Allen may be right, but the evidence 
and weight of authority are decidedly against him. 
In conclusion, I would renew my testimony as to the great merit 
of Mr. Allen’s work, and I only regret that I cannot entirely con- 
cur with him. Although Mr. Allen has not really met the objec- 
tions urged against his views, it might not be obvious to all that 
he has not, and there might be those who would take for granted 
the proposition that I had “fallen into several by no means unim- 
portant errors.” I leave the decision on this charge to the scien- 
tific public. And as there seems to be some danger of the real 
questions at issue being obscured by side issues, I beg to restate 
them. They are :— 
Ist. Are the groups Trichophocine and Oulophocine entitled to 
the rank of subfamilies on account of the characters assigned ? 
2d. Is Zalophus a natural associate of Otaria and Eumetopias 
in a homogeneous and natural group to be contrasted with the 
Oulophocine ? 
Everything not bearing on these is irrelevant. 
As may be perceived, the consideration of the question of the 
values of characters has been distinctly varied by Mr. Allen, and 
the discussion shifted to the question of the existence of some of 
the distinctive characters employed for the differentiation of the 
Trichophocinee and Oulophocine. I will therefore repeat my orig- 
inal admission that the Trichophocine (after the elimination of 
Zalophus) and the Oulophocine are natural combinations, but not 
subfamilies, definable by the characters used by Mr. Allen. — THE- 
ODORE GILL. 
-~ Tue Gerorocy or Iowa.*— These two elegant volumes are the 
‘results of examinations and observations made within the years 
1866, 1867, 1868, and 1869.” The first volume contains in the first 
part an account of the physical geography and surface geology by 
Dr. White, with a chapter on the climate by T. S. Parvin. 
The second part describes the general geology of the state, in- 
cluding the Azoic, Lower and Upper Silurian, Devonian, Carbon- 
iferous, and Cretaceous Systems, the chapter on the middle Coal 
Measures by O. H. St. John. The third part embraces the county 
and regional geology, which is completed in the second volume, 
* Report on the Geological Survey of the State of Iowa. By Charles A. White, M. 
D.; Orestes H. St. John, assistant; Rush Emery, chemist. 2 vols. 1870. Royal 8vo, 
Des Moines. With plates and maps. 
AMER. NATURALIST, VOL. V. 16 
