1896.] ANATOMY OF PETROGALE XANTHOPUS. 699 
border into the cartilages of the second, third, and fourth ribs. 
It has a few indistinct intersections. 
The Pyramidalis rises from the inner side and tip of the mar- 
supial bone, and from the fascia over the lower part of the rectus. 
About midway between the pubes and xiphoid it blends with the 
linea alba. 
__ The Supracostalis rises from the sternal ends of the cartilages of 
the 3rd, 4th, and 5th ribs, and is inserted into the first rib just 
external to the attachment of the rectus. It is well marked, and 
continues the plane of the external oblique, lying between the 
rectus and the pectoral. 
The Quadratus lumborum is present, but is extremely difficult to 
separate from the erector spine. 
The Psoas parvus is very large, and rises from the bodies of all 
the lumbar vertebre except the last; it is inserted into the pro- 
minent ilio-pectineal eminence. 
The Psoas magnus is smaller than the last, and rises from the 
_ transverse process and side of the body of the last lumbar vertebra, 
as well as from the anterior part of the sacrum; it joins the 
iliacus to form a very broad ilio-psoas, which is inserted into the 
flat lesser trochanter. 
Muscles of the Tait. 
These muscles are by no means easy to distinguish one from the 
other, but the following seems the most satisfactory division. 
The Extensor caudce externus rises from the accessory processes 
of all the lumbar vertebra, from the sacrum, and from the caudal 
vertebre nearly as far as the middle of the tail. The tendons, 
which are very long, are inserted into the transverse processes of 
the caudal vertebree, those which rise most anteriorly being inserted 
first. Meckel’ describes this muscle as being distinctly divided 
into two in the Kangaroo, but I was unable to make out the 
division satisfactorily. i 
The Extensor caude internus is fleshy, and rises from the spines 
of the sacral and caudal vertebre; short tendons pass to the 
transverse processes of the vertebre close behind. 
Yhe Abductor caude externus rises from the ischium, and is 
inserted into the transverse processes of the 5th, 6th, aud 7th 
caudal vertebre. 
The Abductor caude internus is simply a continuation of the 
intertransversales muscles. 
The Flecvor caude externus comes from the ventral surface of 
the sacrum and tail, and is inserted into the ventral surface of the 
transverse processes by long tendons, which are arranged in the 
same wanner that was noticed in Sphingurus "—that is to say the 
most superficial tendons are first inserted, and the deeper ones 
reach the surface round the inner side of these. 
1 «Anatomie comparée,’ vol. vi. p. 177. 
2 “ Myology of Rodents,” P. Z.S. 1894, p. suger 
