Mr. P. R. Lowe on the Crab-Plover. 333 



this respect between Larus and Stercorarius is noteworthy, 

 and I have ahxady called attention to it in ' The Ibis ' (J. c). 



Quadrate. — In all the groups that have been discussed, 

 including Dromas, the quadrate has its own peculiar and 

 distinctive characteristics. The orbital process of the 

 quadrate in Dramas is very similar to that of Stercorarius. 

 The quadrates of Haematopus and Chionis both agree in being 

 relatively and actually longer than in either of these last- 

 mentioned genera. la Dromas there is a foramen, leading 

 into a pneumatic chamber, on the inner surface of the body 

 of the quadrate. In Larus it is noticed on the posterior 

 surface. In the Skuas there is also a foramen on the inner 

 surface, but it is placed lower down than in Dromas^ just 

 above the quadrato-pterygoid articulation. Such precise 

 and apparently meaningless, and probably useless, distinc- 

 tions in regard to a small point such as this, compels the 

 thought that such differentiations could hardly have been 

 brought about through the process of continuous variations. 

 The constancy of the precise position of these quadratal 

 foramina in a series of skulls of any groups selected, e. g. 

 the Gulls or the Skuas, is very remarkable, no matter what 

 genera are taken in either group. 



Antorbital Plate. — In Dromas this is a strongly ossified, 

 triangular or ear-shaped process. So it is in Larus; but in 

 Dromas the descending process of the lacrymal approaches 

 this extension of the pre-ethmoid at a different angle (see 

 under " Lacrymal "). 



Turbinals. — In Dromas a prominent bridge of bone pro- 

 ceeds from the superior border of the antorbital plate, to 

 fuse with the outer rim of the external and superior border 

 of the pre-ethmoid. It is continued forwards as a thin 

 turbinal plate, which is ossified. A very similar arrangement 

 is seen in Larus and Stercorarius. Mesiad of the above- 

 mentioned bridge is seen a foramen for the olfactory nerve. 



Interorbital Septum. — The fenestra in Dromas are some- 

 what peculiar, but, on the whole, are reminiscent of what 

 obtains in Squatarola, except that the lower and largest 

 fenestrum is quadrangular. 



