268 Mr. Stmmonns’s Observations 
CHARADRIUS CALIDRIS. 
I observed this species at the Mull of Cantire. 2d June. 
ANAS MOLLISSIMA. 
Most plentiful, it is said, at Papa Westray. I found a nest 
at Pentland Skerrie, very near-the lighthouse. 
Mercus SERRATOR. 
On the fresh-water lochs in the Isle of Glass. "This specimen 
agrees with the description of the adult male, except that the 
head is variegated with dull ferruginous. 
The trachea determined the species and sex. 
Mercus MERGANSER. 
It will perhaps appear presumption to attempt to remove those 
doubts respecting el and the Dun-Diver, which have so long 
existed. 
The following reasons seem almost convincing that tbe M. Mer- 
ganser and Castor are merely varieties of the same species, de- 
pending upon the age and sex. The trachee of the males, the 
vertebrze of the neck (which vary much in aquatic birds), and 
the intestines, in structure, number, and dimensions, are ex- 
actly similar in both. One specimen, shot last April, resembled 
in general plumage the .M. Castor, except that there was little or 
no crest, and the head was much variegated with black. "Two. 
specimens of M. Merganser, and two of M. Castor, now at 
Edinburgh, have each only eighteen feathers in the tail. 
This bird is not scarce in Scotland during the winter season. 
It is called the Skeldrake, and is confounded probably with Anas 
Tadorna, which is more frequently met with in summer. _ 
TETRAO: 
