210 MR. F. E. BEDDARD OX THE [Feb. 19,. 



In another example of Dolichotis 'patacltonka, the conditions 

 observed were a little different. The azygos proper was only to 

 be found on the right side of the body, in correspondence with the 

 fact that this rodent has but one jugular vein. In front of the 

 azygos are two sepai'ately arising superior intercostal veins. On 

 the left side the vein described in the first specimen of Dolichotis 

 also existed, but was of much more limited extent than in that 

 individual. It corresponded in place of origin with the upper of 

 the two separate superior intercostals of the right side. The 

 vessel divided into two branches only, of which one was behind 

 the point of emergence of the vein from the jugular. It is clear 

 that this trunk is the same as that which in the other specimen 

 takes up the place of the azygos of the left side of the body, though 

 it is much less extensive. There is thus no essential difference 

 in respect of the veins of the intercostal system between the two 

 individuals. Only a diffei-ence of degree in the development of 

 the same, and that a slight one. 



The Porcupine {Hystrix cristata), belonging as it does to the 

 same subdivision of the Rodents as the Patagonian Cavy, natui'ally 

 shows some resemblances to that rodent in the disposition of the 

 azygos veins. The right-hand trunk is the chief one to be 

 developed *. In front of it, however, arise from the right jugular 

 separately two intercostal veins. The main trunk gives ofi' first 

 a branch which supplies one rib. This is followed by a more 

 important branch which supplies three intercostal spaces as does 

 the corresponding vessel in Dolichotis. After this the branches 

 are single. On the left side of the body the vena cava anterior 

 sinistra (the left jugular) givesoff two vessels following each other 

 which arise at about the same level as the two biunches of the 

 right jugular which lie in front of the azygos proper. The second 

 of these is the most important, and runs for some distance down 

 the body, giving ofl" four branches to the intercostal spaces. All 

 these lie posteriorly : there is no forward continuation of the vein 

 such as occurs in Dolichotis ; but the forward extension of the 

 vein in Dolichotis is evidently replaced in Hystrix by the separate 

 twig arising from the left jugular. 



In a second example of Hystrix cristata, a male, the arrange- 

 ment of the azygos veins (text-fig. 72) was apparently identical. 

 I use the word "apparently" because in the first example I did 

 not count the ribs between which the various bi-anches of the 

 azygos ran. In the second specimen the azygos flowed into the 

 right jugular at a point on a level with the interval between 

 the third and fourth ribs. The first branch, exactly in the same 

 way as in the example I have just described, supplied three 

 intercostal spaces, beginning with the third rib. A superior 

 intercostal vein arose from the jugular in front of this, and 

 received from the first and second ribs a branch each. On the 

 left side the azygos proper was very slender, but supplied ribs 



* Parsons (P.Z. S. 1894, p. 685) states that there is "only one azygos vein " in 

 Atherura africana. 



