8 Shufeldt, Osteology of Orthorhamphus magnirostris. l^^^y^^, 



for in all these Stone-Plovers it usually presents but a single, not 

 large, vacuity near its centre, while in typical Plovers the partition 

 is quite deficient, in so far as it is preformed in bone. 



Owing to the kind of lacrymal our subject possesses, the orbital 

 roof is likewise more complete and protective, in so far as the 

 eye is concerned, in the Stone-Plover, the Chilean Lapwing, and 

 some limicoline birds than it is in Lams, Rissa, and some of their 

 near congeners. 



Most Gulls, Oyster-catchers, Plovers, Lapwings, &c., have more 

 or less perfectly ossified pars plancB forming the anterior walls 

 of the orbits.; and it is interesting to note that this osseous 

 partition, dividing, in a way, the orbit from the rhinal chamber, 

 upon either side, is present in (Edicnemus, but entirely absent 

 in Orthorhamphus magnirostris and in Chiornis, in which forms 

 these wings of the mesethmoid are found to be only in membrane. 



Owing to the formation of the crotaphyte fossae, and the con- 

 spicuous post-frontal and squamosal apophyses with the deep 

 valley between them, the entire facies of the lateral aspect of the 

 cranium in Orthorhamphus comes closer to some of the Gulls than 

 to any of the true Plovers. In Qidicnemus bistriatus the post- 

 frontal process is very long and slender, almost reaching to the 

 squamosal one below it ; while in average Plovers, including the 

 Lapwings {Vanellus, &c.), these lateral processes of the cranium 

 are invariably short and inconspicuous, with the valley between 

 them usually quite shallow. 



The zygoma or quadrato-jugal bar is rather broad and compressed 

 from side to side, its deepest part being the maxillary extremity, 

 situated between the descending limb of the lacrymal and the 

 nasal of the same side. This is the form of the infra-orbital bar 

 in Lams argentatus, while in the typical Plovers {Squatarola, &c.) 

 and the Lapwings it is very straight, slender, and uniform in its 

 proportions, and its anterior extremity is in a much higher plane 

 than the posterior (the long axis of the skull being held 

 horizontally). 



Lartis argentatus, when adult, possesses, upon either side, an 

 elongate, triangular flake of bone, about 7 millimeters long, which 

 is attached by ligament to the hinder extremity of the descending 

 hmb of the lacrymal. It points directly backward, and is there- 

 fore parallel to the zygomatic bar. (Spec. No. 18,204, Coll. U.S. 

 Nat. Mus.) I find no such ossicle as this in the skull of Orthor- 

 hamphus, nor in any of the typical Charadriidce. 



The free vomer, being bifid posteriorly, straddles the anterior 

 sharp apex of the presphenoid. The bone is unusually long, 

 laterally compressed, narrow from above, downwards, and carried, 

 as it gently curves ventrad, to a bifurcated, sharp point in front. 

 This agrees pretty well with what we find in OEdicnemus bistriatus 

 and in the Oyster-catchers, in which last it is more evidently 

 bifid anteriorly. With respect to Larus, beyond the presphenoid 

 the vomer develops lateral wings of moderate width throughout, 

 which are laterally disposed. These do not occur in our subject, 

 nor in the Charadriidce. 



