126 Baron R. K. von Warthausen on the Nidification 



cavity, on pebbles of chalk or fragments of shells. Each of the 

 nests, found on the 27th of July and the 1st of August 1857, near 

 Araarat and Dahalak, contained two new-laid eggs. They have 

 the elongate-ovate or the shorter and somewhat tapering form 

 by which the eggs of Sterna are always distinguished. Their 

 usual length is from 17 to 18 lines, their usual breadth 12 to 

 13 lines; the smallest specimens are 15| to 16 lines long and 

 12| to 13 broad; the largest ones 16 to 17 lines long and 13g 

 broad; the longest ones 18 to 18| lines long and 12| to 13^ 

 broad. The broadest eggs are therefore the shortest, and the 

 longest the narrowest. 



The shell is not shining, is very thin, and weighs from 16 to 19 

 grains; the surface is equally, finely, and prominently granu- 

 lated. The ground-colour is greenish-yellow, greenish-grey, 

 greyish-yellow, rarely light-brown or bluish-white, sometimes 

 with a reddish shade. The spots are sparingly scattered over 

 the shell, with sharp outlines, small, of a grey, brown, or blackish 

 colour, the edges frequently having a violet hue ; some of them 

 are burnt-brown ; the lightest ones are generally the largest, the 

 darkest ones the smallest, in the form of points, streaks, and 

 sometimes of lines. A few only out of about eighty specimens 

 exhibit coarser spots; five are so dark as to resemble those of 

 Sterna hirundo, and a single one has a uniform bluish greenish- 

 white colour. They are all transparent bluish-green on the inner 

 surface. Comparing them with eggs of other species of Sterna, 

 we find the following differences : — 



Their volume is twice or three times as large as that of the 

 eggs of Sterna minuta, the coloration of both being exactly the 

 same. Compared with the eggs of S. arctica and S. hirundo, they 

 are on the average considerably smaller, lighter in weight, difi'er- 

 ently granulated, with paler (less green and brown) and finer 

 markings, — the largest eggs of S. senegalensis, however, being 

 equal to the smallest ones of the two species mentioned. Small 

 eggs of our species are equal in size to, or even surpassed by 

 the large ones of S. hybrida ; but these, collected in N.W. Africa, 

 Hungary, and S. Russia, exhibit the granulations more flattened, 

 the gi'ound-colour much more intense, and the markings con- 

 siderably darker and frequently more crowded. 



