Reviews—Ur. W. H. Dalton—The Geology of Colchester. 279 
plantigrade or subplantigrade (except, perhaps, in the case of Jfesonyx). 
So far as known at present, there is nothing very exceptional in 
the structure of the pelvis or the hind limbs of the European genera. 
But in the American forms Prof. Cope has described some curious 
points of departure from the typical Carnivora. In all the New 
Mexican genera, “the ilium has a well-marked external anterior 
ridge. The ilium has therefore an angulate or convex external face, 
as in Insectivora and Marsupialia, and does not display the usual 
expansion in a single plane of most of the Placentals.” But the 
strong tuberosity present in all the genera in the position of the 
anterior inferior spine is found only in certain Insectivores and 
Lemurs amongst existing Mammalia. In Ambloctonus and Didymictis, 
the femur supports a third trochanter. This is never the case in the 
Marsupialia. In certain Insectivora, on the other hand, such as the 
Hedgehog, the third trochanter, though rudimentary, is quite distinct. 
As a very general rule, the hind-foot, like the manus, was penta- 
dactyle, and plantigrade or subplantigrade. Prof. Cope has described 
a-curious mode of tibiotarsal articulation in some of the American 
genera. The astragalar articular face of the tibia in these “is not 
divided into two oblique fossa by ‘a rounded crest which corresponds 
to the groove of the superior pulley-shaped face of the astragalus.’ 
It is uninterrupted, and more or less oblique in the transverse 
direction ; always so at the posterior border . . . . The astragalns 
Poo ee presents an open angle upward, which separates the 
superior from the oblique internal face. The superior plane is flat, 
but is interrupted on the posterior side by a groove.” 
In the genus Synoplotherium Prof. Cope found “one of the claws 
to be broad and flat so as to be subungulate.” He has also found a 
similar ungual phalange in a New Mexican species of Carnivore. 
“The flat claws of some of the genera,” remarks Prof. Cope, “tend 
to obliterate the distinction between the Unguiculate and Ungulate 
series, but they are not present on all the digits of all the species.” 
M. Gaudry describes an axis vertebra (supposed by him to belong 
to a Hyenodont animal), of which the spine is bighly elevated; its 
summit, instead of being sharp (as in the Carnivora), is depressed, 
broad and flat. He compares it to the corresponding vertebra of 
some Didelphia. But, as noticed by Prof. Huxley, its form is exactly 
similar to that of the axis of some Insectivores, such as the Hedgehog. 
It may be generalized from the form and number of the caudal 
vertebre, discovered in some of the forms, that all the genera had a 
long and large tail. 
REVIEWS. 
aL! Uae 
I.—Memorrs oF THE GeroLogicAL SurvEY OF ENGLAND AND 
Waters. The Geology of the Neighbourhood of Colchester. By 
W. H. Daron, F.G.S. 8vo. pp. 24 (London, 1880.) 
HE tract’ described is embraced in Quarter Sheet 48 S.W. 
of the Geological Survey Map. The London Clay extends 
over the whole district, covered in one or two places by remnants of 
