376 Venous System of Didelphys Marsupialis 
marsupial heart, the other being the absence of the fossa and annulus 
ovalis. 
There is one more topic in connection with the structure of the 
heart that is worthy of mention, since it has been erroneously described 
by Owen, 66, as a constant marsupial character. I refer to the so- 
called bifureated right auricular appendix. It has been described as 
a prominent feature of the heart by Owen in Macropus and Phasco- 
lomys; by Cunningham, 82, in Phalangista vulpina and P. maculata 
and by Parsons, 96, in Petrogale. It has been found by Cunningham to 
be only slightly indicated in Phascogale and by the writer in Didelphys 
(C S., Text Fig. I), and to be wanting by Cunningham in Dasywrus 
and Thylacinus. The investigations of Cunningham have entirely 
disproved the claims of Owen as to the constancy of this character 
for the heart of marsupials, since he found it wanting in Dasyurus 
and Thylacinus. 
A bifurcated right auricular appendix apparently possesses no great 
significance beyond the circumstance that it represents an instance in 
which the free margin of the appendix has become notched or invag- 
inated as the result of its proximity to the root of the aorta. Such a 
notching is not uncommonly met with in the hearts of the higher mam- 
mals, as, for example, in Arctomys monaz,’ in which a well-defined 
bifurcated right auricular appendix may be present. 
THE VEINS OF THE Heap anp Neox. (Teat Fig. 1.) 
There are two precaval veins in Didelphys, and this is the rule in all 
marsupials with the possible exception of Gelideus breviceps, which has 
been described by Forbes, 81, as possessing only one. In Didelphys 
each precava (pre.) begins opposite the first rib and is formed through 
the union of three veins, the V. subelavia (V. s.), the V. jugularis com- 
munis (V. j. ¢.), and a vein which I have designated as the V. costo- 
vertebralis (V. cv.). The tributaries of the precaval veins are as fol- 
lows: (1) A V. mammaria interna (V. mam.) which opens into the 
ventral surface of each precava near its union with the subclavian 
vein; (2) the V. azygos (V.a.), which opens into the left precava about 
opposite the head of the third rib, and (3) the posterior group of 
coronary veins which also open into the left precava, about opposite 
the head of the fifth rib. The right and left precaval veins open into 
the right auricle along its antero- and posterodorsal walls, respectively; 
6 Princeton Morphological Museum, No. 487. 
