]46 



^Ir. P. R. Lowe on the 



Stercorariidie, but in both tliese groups we miss the very 

 promiuent and conspicuous downwardly-projecting tubercles 

 at the postero-external angles of the basi-temporal plate, 

 which are so characteristic of the true Gulls. Thus in 

 this respect the Sheath-bills and Skuas are pluvialine, the 



Text-figure 4 



Palatal views of the skulls of : — A. Chionis alba ; 

 B. Stercorarius a-epidatus ; C. Larus canus. 



ant. typ. rec, anterior tympanic recess ; basi. temp.pl., basi-temporal 

 plate ; m,vp., maxillo-palatine ; vo., vomer. 



postero-external angles of the basi-temporal plate ending 

 in outwardly-projecting and spiculate processes. The basi- 

 temporal and basi-occipital region in the Gulls and Skuas 

 are strongly contrasted. The Skuas come close to the 

 Sheath-bills in respect of the morphology of this region. In 



