482 Mr. P. H. Lowe on the Sit/nijlcance of certain [Ibis, 



the free ends converoe towards the middle line and underlie 

 the vomer, so that that part ol: the vomerine ])rocess is 

 hidden when these structures are viewed from the palatal 

 aspect. The maxillo-palatines in Plucialis are also more 

 shell-like concavo-convex structures (or more scroll-like). 

 The attachment to the palatal process of the premaxilla is 

 less extensive than in Sqiiatarola. 



{g) In Sijuatarola I have noticed that the dentary margin 

 of the premaxilla is not completely fused with the corre- 

 sponding portion of the maxillo-palatine as it is in Pluvialis. 

 This is a Larine as opposed to Pluvialine character. 



(//) In Sqiiatarola the postero-external angles of the hasi- 

 temporal ])late end in two fairly conspicuous downwardly 

 projecting processes of bone. These processes are but little 

 evident in Pluvialis, but are quite characteristic of the 

 Laridfc and Sternidoe. If well-prepared skeletons of the 

 skulls of the two genera under discussion are com])ared, 

 these differences are generally apparent. A similar distinc- 

 tion is noted between Lams and Stercorarius. 



It is obvious, then, that even if we confine ourselves to 

 characters noted in the skull, there are somewhat surprising 

 anatomical differences in the two forms under discussion, 

 especially if those differences are regarded from a generic 

 point of view, and it is remembered that the leading or out- 

 standino; generic character which has been hitherto held to 

 distinguish Squatarola from Pluvialis is the abortive hind-toe. 

 It may well be that a good many of the characters referred 

 to above are proportional characters, but it will be noted that 

 they are proportional chai'acters characteristic of various 

 Limicoline groups, and in this respect Squatarola seems to 

 present a complex of unit characters of a more mixed nature 

 than Pluvialis, a complex now reminiscent of a purely Vanel- 

 line type, now Larine or Tringine or now Charadriine ; so that 

 we might apparently be justified in hazarding the opinion 

 that Squatarola was an older or more generalised type which 

 we might call Pluvialine or Pre-Charadriine ; but to this 

 point I shall return. 



