1121 
show the succession of the various muscles in a longitudinal section 
of the inferior part of the abdomen. 
With Phascologale penicillata (fig. 1c) the following relation exists : 
The inferior portion of the M. obliquus internus inserts itself into 
the lateral border of the Os marsupiale; the superior portion, unable 
to attach itself to the Os marsupiale, extends along the upper border 
of the M. marsupialis and is inserted into the linea alba. Moreover 
a leaf is split from the aponeurosis, which passes with the aponeurosis 
of the M. transversus behind the M. rectus. With Belideus ariel the 
course of the M. obliquus internus and M. transversus was the 
same as with Phascologale. Here also the M. marsupialis lies in 
front of the M. rectus, the muscle-fibers, however, follow a more 
oblique, proximal course than in the case of Phascologale. 
Between M. marsupialis and M. rectus of Petrogale penicillata 
(fig. 1a) runs the anterior leaf of the aponeurosis of the M. trans- 
versus; this splitting into an anterior and a posterior leaf takes place 
only in the inferior portion of the M. transversus. More towards 
the cranium the M. transversus continues unsplit behind the M. 
rectus. The M. -obliquus internus of this animal does not continue 
between M. marsupialis and aponeurosis of the M. transversus, but 
follows the latter muscle behind the. M. rectus. In Petrogale 
xanthopus Parsons ') found nearly the same condition: “The internal 
oblique is inserted into the last three ribs, dorsal to the lateral line 
of the body it is fleshy, while ventrally it becomes aponeurotic and 
blends with the transversalis. The transversalis.... passes-in the 
anterior two thirds of the abdomen deep to the rectus, in the posterior 
third it splits to enclose that muscle”. 
On the M. obliquus internus and M. transversus of Didelphys 
virginiana Erriorr Cours’) writes: ‘‘The lower border (of the internal 
oblique) is fleshy and stretches nearly horizontally inward from 
Poupart’s ligament to the upper part of the marsupial bone, a stout 
bundle of fibres being inserted into the tip of that bone. The rest 
of the muscle passes more and more directly upward, till its 
posterior part is vertical. Its anterior margin ends along a linea 
semilunaris by blending the aponeurosis with that of the transversalis’’. 
Of the latter muscle Cours says: “There is no splitting of the 
aponeurosis to get outside the rectus below” (fig. 10). 
1) Parsons. On the anatomy of Petrogale xanthopus. Proceedings of the Zoolo- 
gical Society of London. June 16, 1896. 
2) Ermorr Cougs. The osteology and myology of Didelphys Virginiana. Memoirs 
of the Boston Society of Natural- History, Vol. Il. Part. 1 1872. 
