444 



Six examples of this type were met with distributed among 

 three males and three females. 



Vi.e.s. 



V 



L.e.s 



Vced. 



Fig. I. 



Fig. 2. 



Fig. 1. Veatral aspect. Adult J» Type I. 



Fig, 2. Dorsal aspect of Fig. 1. 



A.ic. A. iliaca communis. A.i.e. A. iliaca externa. A.i.i. A. iliaca interna. A.m.inf. 

 A. meseuterica inferior. A.m.sup. A. mesenterica sup. Ao. Aorta. A.o.m. A. omphalo- 

 mesenterica. A.p. A. pudenda. A.p.v. A. pudendo-vesicalis A.s.i. A. spermatica interna. 

 A.s.m. A. sacralis media. A.v. A. vesicalis. D.U- Vessel that unites V, iliaca interna 

 with V. iliaca externa, dorsal to the A. iliaca communis. F. Foramen. VU. Vessel that 

 unites Vv. iliacae internae with Vv. iliaca externae, ventral to the Aa. iliacae communes. 

 V.cp. V. cava posterior. V.i.e. V. iliaca externa. V.ii. V. iliaca interna. V.ii.c. 

 V. iliaca interna communis. V.p. V. pudenda. V.p.v. V. pudendo-vesicalis. V.s.i. V. sper- 

 matica interna. V.s.m. V. sacralis media. V.s.r. V. supra-renalis. V.v. V. vesicalis. 



Figures 1 and 2 represent ventral and dorsal views of the same 

 preparation i). 



In Fig. 1 the V. cava posterior is formed by the union of the 

 Vv. iliacae externae with the V, iliaca interna communis, the latter 

 being formed by the union of the two Vv. iliacae internae. All of 

 these vessels which help to form the V. cava posterior unite ventral 

 to the arteries. See Fig. 2. 



InHalmaturus the V. cava posterior is formed by the union 

 of the two Vv. iliacae communes which, on their part, are formed 



1) All of the Figures, unless otherwise stated, were drawn from 

 dissections and represent the veins which, by their union, help to form 

 the V. cava posterior in Didelphys Virginian a. The Figures of 

 Didelphys are three quarters the natural size of the preparations. 

 The veins are in white and the arteries in black. The lettering corre- 

 sponds in all of the Figures, d and s at the end of an abbreviation 

 indicate d extra and sinistra, respectively. 



