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



make an angled knee ; but, whereas in Dromas this back- 

 wardly-directed or distal extremity Las an inward direction, 

 in Larus it has an outward. In Dromas, too, ,the angle 

 made by the proximal and distal halves of the descending 

 process of the lacrymal is much less acute than in Larus, 

 and, as a consequence, the distal end approaches the ant- 

 orbital plate from above, while in Larus it approaches the 

 same structure from well in front (cf. text-figure 10). In 

 both forms we find, projecting forwards from the angled 

 knee, a spinous process ; but, whereas in Dromas it is thin, 

 sharp, and conspicuous, in Larus it is aborted. In all the 

 above-mentioned points the lacrymals of Dromas have a 

 modified pluvialine arrangement in contradistinction to a 

 typical larine. In Heematopus the descending process of 

 the lacrymal makes no such angled knee as described above ; 

 on the contrary, it comes down perpendicularly to fuse with 

 the antorbital plate in the usual pluvialine method. 



In both Dromas and Larus the distal end of the descending 

 lacrymal fuses with the extero-superior angle of the ant- 

 orbital plate of the mesethmoid or with its apex or outer 

 extremity. In the freshly-hatched chick oiDi-omas it fuses 

 with the extero-superior angle. 



Fronto-nasal Region. — Corresponding with the diflierences 

 in the lacrymals in the above forms, we find that there are 

 other distinctions to be noted in the fronto-nasal region. 

 Briefly noted, these are the shorter relative length of the 

 fronto-nasal space in sagittal section in Dromas ; the contrast 

 in the method of articulation of the proximal ends of the 

 nasals (text-figure 10) ; the greater length of the nasal 

 vacuity in Larus and its different shape. 



In both Larus and Dromas we find a schizorhiual 

 arrangement. 



Premaxill(S. — In several respects the upper jaw of 

 Dromas is not pluvialine in form. Neither is it larine. 

 It is, however, very similar to the condition of things to be 

 noted in oedicnemine genera. Its palatal surface (text- 

 figure 11), distad of the point from whence its maxillary 

 processes have an independent existence, forms a continuous. 



