72 



Zoological Society : — 



pected, showing a general resemblance, present the following differ- 

 ences, which are greater than such as are usually found in indivi- 

 duals of the same species. 



When dried, they are of nearly the same length, viz. about 14*5 in.; 

 but the bronchial rings are 1 5 1 in number in P. Riippellii, and only 

 138 in P. gambensis. The tubes are flattened throughout the 

 greater part, becoming cylindrical at 1*5 inch from the lower extre- 

 mity. Here they are much compressed, and develope a large osseous 

 bulb on the left side. The lower portion only of this bulb, as 

 usual, is completely ossified, the upper part being covered with fine 

 framework, which, as will be seen from the accompanying woodcut, 

 assumes a different pattern in the two species. In P. Riippellii (figs. 2 

 and 4) the bulb is wider, higher, and much compressed ; in P. gam- 

 bensis (figs. 1 and 3) shorter and comparatively much thicker. This 

 is particularly observable in the side view, as shown in figs. 3 and 4. 



Fig. 3. 



Fig. 4. 



From Mr. Ey ton's observations (Monogr. Anatidae, p. 79) it is evi- 

 dent that the trachea of the female Plectropterus is, as is generally 

 the case in this sex, destitute of the osseous bulb. 



I have already pointed out the external characters by which the 

 two Spur-winged Geese may be distinguished ; and their synonymy 

 will now stand somewhat as follows : — 



1. Plectropterus gambensis. 



Anas gambensis, Linn. — A, spinosa, Vieill. ; Lath. Gen. Syn. iii. 

 pt. 2, p. 452, pi. 102 ; G. H. x. 241. — Anser gambensis, Benn. 

 Gard. Men. Zool. Soc. ii. p. 207, cum fig. — Plectropterus gam- 

 bensis, Steph. in Shaw, Zool. xii. pt. 2, p. 7, pi. 36 ; Hartl. Orn. 

 West-Afr. (partim) ; Eyton, Monogr. Anat. p. 79 ; Sclater, P.Z.S. 

 1859, p. 131, pi. 152. fig. 2. 



