Systematic Position of the Sheath-bills. 145 



the Gulls, moreover, the antorbital plate has its extero- 

 inferior angle continued downwards and outwards to a 

 pointed process. In the Skuas the antorbital plate is right- 

 angled in shape. 



The " pointed process " o£ the antorbital plate in the 

 Gulls is apparently reminiscent of " a structure of intense 

 interest '' referred to by Prof. W. K. Parker (Trans. Linn. 

 Soc. Lond. 2nd Ser. Zool. vol. i. pt. iii. 1876, p. 150) as the 

 " OS uncinatum.'^ 



In Hcematopus the morphology of the lacrymals and 

 antorbital plates is quite peculiar to itself and very diflFereut 

 from the arrangement seen in the Chionididae, in which, 

 as has been indicated, these antorbital plates are not 

 ossified. 



Shufeldt (/. c.) sees gallinaceous characters in the lacrymals 

 of the Sheath-bills. He says "they are very much like 

 what they are in the Fowls, agreeing with these elements 

 as we find them in any Grouse of the first year, but lacking 

 the peculiar descending spine-like processes of the adult 

 birds ; thus both in Chionis and the Fowls we find the 

 aborted antorbital plates to be in the same case.^' At 

 the risk of appearing hyiDcrcritical, I am obliged to dissent 

 strongly from this point of view, since statements of such 

 a nature, coming from so well-known an authority, are 

 unfortunately copied and perpetuated. In the first place, 

 it may be bluntly stated that it would be difficult to find 

 such strongly difEerentiated lacrymals as those characteristic 

 of the Chionididae and Gallinae ; while, in the second place, 

 we find aborted antorbital plates in the CEdicnemidae. 



Base of the Skull, 



A glance at the accompanying text-figures reveals the 

 fact that, in a general way, the morphology of the basal 

 structures in the Chionididae come closer to the Skuas than 

 to any other group. 



In the Chiouidida3 the mammillated processes at the base 

 of the basi-temporal plate are more prominent than in the 



SER. X. — VOL. IV. L 



