140 Mr. P. R. Lo^ie o« the 



of the supraoccipital and cxocf^i[)ital is completel)' oblite- 

 rated. There are no supraoccipital fenestra. These aie 

 also at)sent in the Skuas and Gulls. They are present in 

 Htematopus and the Plovers (Litiiicolse). 



Parietal Region. — Comparing this region Mith that of the 

 true Gulls (Laridpe) the absence of the deep and conspicuous 

 temporal grooves is at once obvious. Without entering into 

 details, it may be pointed out that the general configuration 

 of the fron to-parietal region in the Sheath-bill generals quite 

 peculiar [cf. text-figure 3), the vault of the skull frontal- 

 wards being prominent, smooth, and high, without any evi- 

 dence o£ sagittal grooving. The morphology of this region 

 differs widely, iu fact, from that peculiar to the Gulls or 

 Charadriidse. A very interesting point is here to be noted, 

 viz., that the deep and prominent temporal grooves so 

 conspicuous in the Laridse are (as in the Chionididse) com- 

 pletely missing in the Skuas, a fact which appears to have 

 been hitherto overlooked. These deep temporal fossae are, 

 for instance, generally quoted as being distinctly larine 

 characters, the word larine being used in a wide sense so as 

 to include the Skuas. As a matter of fact, the depressions 

 for the attachment of the temporal muscles in the Skuas, 

 small in extent as they are, and strictly limited to the sides 

 of the skull (squamosal region, etc.), are even smaller than 

 in the Chionididse ; and in their position and limits are 

 distinctly pluvialine. To be quite exact, however, this only 

 applies to the genus /S/ercoran'w^, since iu MegaJestris we get 

 a stage somewhat intermediate between Stercorarius and the 

 Gulls proper, although even in Megalestris the surfaces for 

 the attachment of the temporal muscles still remain shallow 

 and ungrooved. The importance of these so-called larine 

 grooves as characters which have any I'eal significance in 

 relation to affinities is thus very distinctly diminished, for 

 their presence or absence appears to be more or less a matter 

 of functional stress, or dependent upon the use to which 

 the temporal muscles are put in the process of obtaining 

 food. 



