458 The Lemuroidea and the Insectivora of the [May, 
case a rounded distal extremity, forming part of a cylinder 
directed more or less fore and aft, for articulation with the meta- 
tarsus or proximal element of the great toe. In the Insectivora 
this structure is wanting, the inner toe being fixed in a position 
parallel with the others as in the Carnivora. In the Lemuroidea 
the position of the thumb or pollex is less different from what 
is seen in the Insectivora, than is the case with the posterior foot. 
In the true lemur the thumb is but little opposable, except in the 
genus Chirogaleus and some others. The distal end of the tra- 
pezium bone of the carpus with which the thumb articulates, does 
not form a part of acylinder in the Lemur or in the Tarsius. 
When the thumb becomes opposable in the monkey proper, the — 
thumb facet of the trapezium is not rounded, but is wide and a 
little concave. It is not till we reach the man-like opposable 
thumb of the anthropoid apes that we find this bone presenting 
to the thumb a semicylindrical face like that of the entocunei- 
form bone of the posterior foot. 
The Condylarthra as I have pointed out must be regarded as 
a division of the order of Taxeopoda, along with the Hyracoidea, 
the lemurs, the monkeys and man. The difference between the 
hoofs of Phenacodus and the ungues of Lemur is too slight to 
admit of wider separation: and the other parts of the structure 
show an equal agreement. There is no trace of opposability of 
the hallux in Phenacodus however, nor any os centrale of the car- 
pus, characters which show that the suborder Condylarthra and - 
Lemuroidea are distinct. In the pollex or thumb of Phenacodus, 
however, there is a distinct indication of opposability, though it 
is not so well developed as in the genus Lemur. The basal artic- 
_ulation with the trapezium is narrow, but is directed partly fore 
and aft, so that the thumb looks inwards. Its power of flexure 
at the base has been slight, but the flexure at the base of the first 
phalange has been such as to make the end of the thumb quite 
opposable? From the Condylarthra then we trace the order 
Quadrumana on the one hand, and the hoofed orders on the other. 
_ In the following pages I will not attempt to distinguish which 
of the genera are lemuroid and which are insectivorous, since the 
phalanges are yet unknown. An exception must be made 
in ‘the case of the genus Pelycodus, where a single compressed 
| -P NATURALIST, April, 1885. Primates and Taxeopoda are there regarded as 
~ ŽSee NATURALIST, 1884, Plate xx1x, for the skeleton of Phenacodus.  * 
