1125 
The lower portion of the M. obliquus internus is inserted into 
the lateral border of the Os marsupiale; the lower portion of the 
M. marsupiale arises from the medial border of this bone. The 
aponeurosis of the middle part of the M. obliquus internus does 
not continue as far as the linea alba, but blends with the upper 
portion of the M. marsupialis, so that this part of the aponeurosis 
constitutes an intermediate tendon between the two muscles. The 
upper part of the M. obliquus internus is inserted into the linea alba 
and the lower ribs. Here, then, there is a close relation between the 
two muscles, so that it might be called a Pars marsupialis musculi obliqui 
interni. But in most cases the relation 
between the two muscles is less distinct. In 
the description Vrom gives us of Dendrola- 
gus inustus, alluded to above, we read 
that “Zij (de buidelspier) hecht zich aan 
de witte lijn en slaat zich achter het 
marsupiaalbeen om ten einde zich te ver- 
eenigen met de peesplaat van M. obliquus 
internus en transversus.” True, this des- 
cription falls short of clearness, but it is 
not impossible that in Dendralogus a con- 
dition occurred such as I observed in 
_Didelphys marsupialis. 
Various opinions are prevalent concern- 
ing tbe Ossa marsupialia. FLowsr *) 
considers them as “Verknöcherungen der 
inneren Sehne der äusseren schrägen 
Bauchmuskel selbst, oder doch innig mit 
ihr verbunden, und sie fallen daher unter 
der Kategorie der Sesam beine’”’. Karz ”) 
diene speaks of “Ossificationen in einer hintern 
sehnig gedachten Partie des M. Pyrami- 
Fig. 2. dalis”. Since Wri1epersnurm °) undertook 
his extensive inquiries into the pelvic girdle, it is generally received 
that the Oss marsupiale is a strongly developed Epipubis. In the 
matter of homology of M. pyramidalis and M. marsupialis, the 
significance of the Os marsupiale is immaterial. 
1) Flower. Einleitung in der Osteologie der Säugethiere, 1888 p. 298. 
*) Karz. Zur Kenntniss der Bauchdecke und der mit ihr verknüpften Organe bei 
den Beutelthieren. Zeitschrift fur wiss. Zoöl. Bd. 36. 1882. 
3) WrepersHerm. Die Phylogenie der Beutelknochen. Zeitschrift für wiss. Zoöl. 
Bd. 53—1882. (Suppl.). 
