180 MR. F. G, PARSONS ON THE [Jan. 14, 
and Bathyergus the straight head was reduced to a minimum; the 
reflected head has usually some fleshy fibres rising directly from it. 
With regard to the other muscles the vastus externus is large and 
separate, while the internus is small and closely blended with the 
crureus. 
Adductors.—The adductor mass in the Myomorpha resembles in 
its complexity that of the Sciuromorpha, although one frequently 
finds attempts at the more simple arrangement of the Hystrico- 
morpha by fusion or non-differentiation of contiguous parts. As 
in the other Rodents, the supracondylar slip has been described 
with the semimembranosus, to which it undoubtedly belongs. 
Perhaps the animal which shows the greatest differentiation is 
Cricetomys: in it the mass consists of the following parts: (1) The 
most anterior portion from the ilio-pectineal line to the middle 
of the posterior border of the femur by a narrow flat tendon. 
(2) Deep to this is another bundle which has the same origin but 
comes from rather more of the symphysis and goes to the whole 
of the femur as low as the ligamentum patelle. (3) Behind the 
last is a thin flat portion rising by tendon from the horizontal 
ramus and being inserted into the lower half of the femur. 
(4) Most posteriorly, there is a thick mass from the ramus and 
tuber ischii which is inserted into the whole length of the back 
of the femur from the insertion of the quadratus femoris to the 
internal condyle. 
In Cricetus (1) and (2) are fused and (4) only goes to the upper 
half of the femur. In Microtus (1) and (2) are fused, as are also 
(3) and (4). In Gerbillus, Mus barbarus, and Mus rattus (3) was 
not identified, while (4) was only inserted into the upper half to 
two-thirds of the femur. Rhizomys closely resembles Cricetomys. 
In Georychus and Bathyergus (1) is inserted into the middle third 
of the femur behind the pectineus, while the other three parts are 
fused into one great mass, which in Georychus is inserted into the 
middle two-fourths of the back of the femur, while in Buthyergus 
it goes to the whole length of that bone. In Hydromys, according 
to Windle, the adductor magnus, which apparently corresponds 
to the part which I have described as (4), reaches as low as the 
head of the tibia *. 
Tibialis Anticus——This muscle always has the human origin ; it 
never rises from the femur as in some of the Hystricomorpha. 
In Georychus the tibia above the cnemial crest is flattened, and 
forms a triangle with the apex downward and the surface a little 
concave; from this the muscle rises. As a rule, the tendon divides 
slightly below to be inserted into the internal cuneiform and the 
base of the first metatarsal, the latter insertion being the smaller. 
In Merotus, however, the tendon divides into two equal parts. 
In Gerbillus, Mus barbarus, Mus rattus, and Myodes the tendon 
does not divide at all, but goes entirely to the cuneiform. In 
Heteromys the division is well marked, but both parts are inserted 
into the cuneiform. 
1 P.Z.8. 1887, p. 58. 
