442 



die V. cava posterior ein. Erwähnenswert wäre ferner noch ein den 

 Ureter begleitender Venenplexus, welcher sein Blut in die V. renalis 

 ergießt." 



The above description for Halmaturus applies to the V. cava 

 posterior of all the Marsupials examined by Hochstetter with the 

 exception of that ofPetaurus taguanoides in which the V. cava 

 posterior possesses the same relations as in the cat. 



An examination of twenty six specimens of D i d e 1 p h y s v i r - 

 giniana (eleven half grown and fifteen adults) has shown the 

 writer that the V. cava posterior in this animal agrees only in the 

 following particulars with the description given above by Hoch- 

 stetter for this vessel in Halmaturus: In each, the relative 

 position with respect to the Aorta and the general course of the V. cava 

 posterior is the same; in each animal the Vv. spermaticae open into 

 the V. cava posterior about midway between the Vv. renales and 

 the Vv. iliacae externae; also a vein which accompanies the ureter, 

 on each side, extends between the V. spermatica and the V. renalis. 

 In all other respects, especially in its mode of origin, 

 the V. cava posterior of D i d e 1 p h y s differs in marked respects from 

 that of Halmaturus. In fact, the mode of origin of the 

 V. cava posterior in Didelphys was found to be so 

 variable in the twenty six different individuals ex- 

 amined, that it is quite impossible to assign any one 

 mode of origin for this vessel which may be regarded 

 as typical for the species. 



For descriptive purposes the various modes of origin of the 

 V. cava posterior of Didelphys vir giniana are classed under 

 three main Types as follows: 



Type I. Those cases in which the Vv. iliacae in- 

 ternae unite with the Vv. iliacae externae to 

 form the V. cava posterior, ventral to the A a. 

 iliacae communes or ventral to the Aorta. 

 Type II. Those cases in which the V v. iliacae i n - 

 ternae unite with the Vv. iliacae externae to 

 form the V. cava posterior, dorsal to the Aa. 

 iliacae communes or dorsal to the Aorta. 

 Type III. Those cases in which the Vv. iliacae in- 

 ternae unite with the Vv. iliacae externae to 

 form the V. cava posterior, both dorsal and ventral 

 to the Aa. iliacae communes or both dorsal and 

 ventral to the Aorta. 



