234 ANATIM. 



The organ of voice appears, from one that I examined, 

 to be like that of the Mute Swan ; but Mr. Pelerin has 

 found considerable differences in various parts of the head ; 

 the description and measurements were given in a paper 

 published in the Magazine of Natural History for 1839, 

 page 178, from which the following is an extract. 



" The measurement of an adult cranium of each is as 

 follows : Length, from the tip of the bill to the base of 

 occipital bone in C. immutabilis, six inches and three- 

 eighths; C. olor, six inches and seven-eighths. Height, 

 from the bottom of the lower mandible when closed, to 

 the top of the protuberance at the base of the bill, in C. 

 immutabilis , one inch and five-eighths ; C. olor, two inches. 

 Height, from the base of the under jaw to the vortex of 

 the head, just behind the orbit of the eye, in C. immu- 

 tabilis, two inches and one-eighth ; C. olor, two inches and 

 a quarter. In C. immutabilis the bill is rather more 

 flattened, particularly in the middle, between the dertrum, 

 or nail, and the nostrils ; the protuberance at the base of 

 the upper mandible is less developed. In the Polish Swan 

 the cranium is highest at the supra-occipital portion ; in 

 the Mute Swan the cranium is highest at the supra-orbital 

 portion ; but the greatest difference is perceptible on com- 

 paring the occipital bones ; the upper portion of this bone 

 in C. immutabilis protrudes considerably more, and there 

 are two oval foramina, one on each side just above the 

 foramen magnum, which are not present in any specimens 

 of C. olor that I have examined ; the portion forming the 

 boundary of the external orifice of the ear is much more 

 prominent, and the condyle forms a more acute angle with 

 the basilar portion of the occipital bone.'* 



I have verified all Mr. Pelerin's observations. 



