1 Shufeidt, Osfeolooy of OrtlKtrhdinf^lius iiui^iiiros/yi^ 



21 



there is only a narrow lendinal t^rooxc niniiin.i,^ down the proximal 

 half of the shaft. 



Hypotarsiis is short and quadrilateral in form. It is composed 

 of an outer and an inner })ortion. the latter heing the longer of 

 the two. They are joined su})eriorly by a transverse, osseous 

 bridge, which is longitudinally i)ierced by a single tendinal foramen. 

 This passes into the valley or groove which stands between the two 

 crests of this hypotarsial projection distally. 



The usual two foramina are found on the anterior aspect of the 

 shaft, side by side, just above the small, low, elongate ridge upon 

 which the tendon of the tibialis anticus muscle is inserted in life. 

 These foramina pass directly through the shaft of the bone, one 

 api)earing upon either side of the hypotarsus ])osteriorly. 



At the summit of this bone, the intercondylar tubercle is con- 

 spicuously developed, and the condylar depression upon either 

 side of it is somewhat deeper than we usually find it in many 

 birds. 



Distally, the three trochlear processes are of large size, as com- 

 pared with the shaft that supports them. The inner one is the 

 most elevated, and projects next farthest ])osteriorly, as com- 

 pared with the one for the outer toe, which slightly exceeds it in 

 this respect, and is situated nearly as high on the shaft. The 

 largest trochlear projection is the middle one, and it is at the 

 same time the lowermost on the tarso-metatarsial shaft. 



This bird possesses no hallux, and the first metatarsal is entirely 

 absent, which is also the case in Gidicneniiis histriatus, in which 

 species the tarso-metatarsus, being considerably longer than it is 

 in Orthorhamphus, agrees with it otherwise very closely in the 

 foregoing characters. 



There is no especial agreement between this tarso-metatarsus 

 of Orthorhamphus and the same bone in any of the LaridcB or in 

 Hamatopus, and still less in Chionarchus ; while, upon the other 

 hand, it holds many characters in common with the tarso- 

 metatarsus of the Chilean I.apwing (Belonopterus), and in all likeli- 

 hood with other Charadriidce. In most of the limicoline forms, 

 however, the hypotarsus is different ; for, while short and of 

 approximately the same form, it is generally twice grooved 

 posteriorly instead of only once, as it is in Orthorhamphus. 



Sesamoidal bones of various sizes according to their location 

 occur at the plantar extremities — both distal and proximal — of 

 the basal phalanges of pes. the largest and most important one 

 being situated in the " sole of the foot " at the proximal end of 

 the basal joint of the mid-anterior toe. where it covers entirely 

 the plantar aspect of the mid-trochlear }:)rocess of the tarso- 

 metatarsus. 



The phalanges of pes (Plate VI.. fig. ii) are stouter, joint for 

 joint, than the corresponding ones in the foot of (Hdicnemus 

 bistriatus. the arrangement being the same in both birds — that 

 is. 5. 4, and 5 joints to the second, third, and ftnu'th foes respect- 

 ively, or the inner, middle, and outer ones. 



