212 MR. F. E. BEDDARD ON THE [Feb. 19, 



azygos presents no features of any special interest ; it is like that 

 of many other animals. In front are two separately arising 

 superior intercostals. The difierence between these veins in the 

 present genus and in the true Old World Porcupines is one 

 more justification of the absence of near affinity between those 

 superficially similar rodents. I examined two specimens of this 

 species. 



Myopotamus coijpu has two jugulars, and there is an azygos 

 vein opening into each at the same level. That of the right side 

 of the body is the one which is fully developed and runs a long 

 way down the body. On the left side a slender twig joins the 

 jugular of that side which appears to emerge from one intercostal 

 space only. The arrangement of these vessels in the Chinchilla is 

 the same. 



In Lepus europceus, Arctomys marmotta, Cynomys ludovicianus^ 

 Lagomys roylei, there is but one azygos and that on the right side 

 of the body. 



In Sciurus hicolor there are also two jugular veins as in the 

 species which have just been described. There is also in the same 

 way but a single azygos vein arising from the i-ight jugular. The 

 branches of this vein are collected from the series of intercostal 

 spaces commencing with that lying between ribs 4 and 5. 



Sciurus maximtis differs from the other Squirrel mentioned in 

 the present communication in that there is but a single jugular 

 vein, which is the right-hand one of other Squirrels. Into this 

 opens the well-developed right azygos vein, which presents no 

 differences from that of other members of the genus Sciurus, 

 ■except of the smallest detail. Its affluents commence with that 

 of intercostal space 5/6, Corresponding to this vein, however, 

 there is a very small left azygos. This vein collects blood only 

 from ribs 4 and 5, and it opens into the single jugular just a 

 trifle in front of the point of opening of the large right azygos. 

 The right azygos, I should add, in both the species that have just 

 been referred to extends back considerably fui'ther than the 

 last rib. 



Of Sciurus vulgaris I have examined two individuals, one a 

 male and the other a female. The two agreed in every detail of 

 structure. This species belongs to that group of the rodents which 

 possess two jugulars. But in spite of this the azygos vein is 

 single and is present on the right side only. I did not observe 

 any superior intercostal vein arising from the jugular in front of 

 the point where the ti-ue azygos spi'ings. I found the same to be 

 the case with Sciurus palmar um. 



In ffydrochcerus capybara there are similarly two jugulars and 

 only a single azygos, which as in Sciurus is on the right side of 

 the body. There was nothing to be seen of an azygos on the left 

 side, which is pei-haps remarkable in view of the relationships of 

 this rodent. This statement moreover applies to two examples of 

 the species. 



In the Jerboa, Jaculus orientaUs, a rodent with two jugulars 



