248 ` The American Naturalist. [March, 
geologists who supposed that Major Powell had abandoned his extraor- 
dinary position on the question of coloration of geological maps. We 
seem to see in Florida a good representation of the Archean, Paleozoic 
and Mesozoic beds, as well as the Cenozoic. For this Mr. Dall is in 
no way responsible. It is a pity that expense should be incurred in 
printing such maps, since they will have to be republished with the 
customary colors. 
Cary on the Evolution of Foot Structure.’—We have in this 
paper a study of the fore foot of Palseosyops, from a specimen in 
the museum of Princeton College, conducted with a view of ascertaining 
the mechanical relations of the parts when in action. The ultimate 
object is to determine whether the structures presented (facets, etc), can 
have been produced by direct mechanical impacts, strains, ete., as is 
alleged by the Neolamarckian school of evolutionists. The study is 
conducted with care, so far as it goes, but it is not always easy to under- 
stand the drift of the author’s argument. He reaches but one definite 
conclusion, viz.; that the trapezoid is too small to express properly a 
result of direct mechanical causes. This fact, the author says is 
incompatible with the Lamarckian principle. He informs us that in 
reaching this result he has applied geometrical methods. “ First, the 
volume of the bones was got at. Next the area of the bearing surfaces 
and their inclination to the digits were measured. Then giving to the 
thrust of each metacarpal a value proportional to its volume, the distri- 
bution of that thrust can by resolution and composition of forces, be 
traced through the foot, and the pressure on each surface and bone 
approximately obtained.” Further than this the author does not 
explain how he reached the result that the trapezoid is too small. It 
is quite essential that this demonstration should be given if we are 
expected to accept his conclusion. An essential part of the problem 
is, however, unnoticed by Mr. Cary; and that is the condition of the 
trapezoid in the reptilian ancestors of the Mammalia. The phylogeny 
of an element must be known, since it furnishes the “ physical basis” 
of the problem. 
. Cary then proceeds to criticize the explanations offered by 
Professor Osborn and myself, in accounting for the origin of certain 
structures. He finds our explanations to be self-contradictory, and 
that we also contradict each other. Osborn has supposed that the 
conules of the molars are produced by friction of the molars of opposite 
šA study in Foot Structure; by Austin Cary. American Journal of Morphology 
Dec. 1892, p. 305. 
