Mr. P. R. Lowe on the Crab-Plover. 329 



though slightly hollowed bridge from one cutting-edge of 

 the tomium to the other; and in this respect it agrees 

 with all the Stone-Plover genera, but more especially witli 

 Orthorhamphus. 



As in these oedicnemine genera, the palatal surfaces of 

 the maxillary processes of the prem axillae are flat, broad, 

 and ribbon-like. 



In the CharadriidcC, such as Squatarola and Pluvialis, the 

 palatal surface of the premaxillse is not bridged in the above 

 fashion, with the result that a distinct groove is left between 

 the tomial edges right up to the very tip of the bill. In 

 the Gulls (Laridse) and Skuas (Stercorariidse) a modifica- 

 tion of this bridge is seen which is quite distinctive, while 

 in both the Sheath-bills (Chionididse) and the Oyster-catchers 

 a condition of the hard palate peculiar to either group is 

 again seen. 



Taking a general view of the premaxillse of Dromas and 

 Orthorhamphus the resemblance in morphological details is 

 very striking, but since Orthorhamphus is peculiar among 

 the Stone-Plovers in leading a littoral existence, and indeed 

 in making its nest on the actual shore, this resemblance 

 does not warrant any deductions as to a like affinity, and 

 may be ascribed solely to functional stress. 



The Base of the Skull. — In Dromas there is a somewhat 

 deep and distinctly defined cordiform pre-condylar fossa 

 (text-figure 11). The basi-temporal plate is thin and equi- 

 lateral, its surface being smooth and grooved in the sagittal 

 axis, while its postero-external angles do not terminate in 

 the downwardly projecting processes so characteristically 

 seen in the Gulls and Terns. 



In place of these we observe in Dromas a sharp spur-like 

 or pointed process, directed outwards and backwards, a 

 condition which is more perfectly seen in the Skuas and 

 less perfectly in the Golden Plover. Curiously enough, the 

 downwardly projecting processes so characteristic of the 

 Laridse are to be noticed in Squatarola, while they are 

 present in some Stone-Plover genera (^(Edicnemus) and 

 iibsent in others [Orthorhamphus). 



