394 ME. R. W. H00LEY ON THE [Julie 1915, 



are placed vertically. No rising of the alveolar rims. Anterior 

 nares large, oblique, looking outwards, near the tip of the muzzle, 

 and separated from the antorbital vacuity. The antorbital vacuity 

 is the largest fossa in the skull, and not confluent with the orbits. 

 Orbits very small, circular, and placed far back in the head. 

 Orbital rim incomplete. No sclerotic ring. Infratemporal fossa 

 oblique, extending both in front and behind the orbits. A sixth 

 vacuity (infra-orbital) occurs under, and confluent with, the orbits. 

 The beak, anterior to the nares, and the brain-capsule are the only 

 portions of the skull that are completely encased in bone. Dorsal 

 bar ridging nares and antorbital fossse, triangular, with no lateral 

 expansion. The jugal is entirely separated from the supra-temporal 

 arcade, and the jugal and quadratojugal from the infra-temporal 

 arcade. The jugal forms merely a small moiety of the anterior 

 border of the orbit, and is connate, at its lower extremity only, 

 with the quadratojugal and quadrate. The jugal, quadratojugal,. 

 and quadrate are directed obliquely backwards ; all connect with 

 the maxilla. The quadrates articulate with the lower jaw, far in 

 advance of the orbits, by plain pulley-joints. The lower temporal 

 arcades are formed entirely by the quadrates. Length of sym- 

 physis=70 mm. Six vertebrae in the notarium ; no supra-neural 

 plate. The transverse processes are free from each other ; the 

 anterior and posterior pairs are of the same length, the median 

 shorter and smaller. Six free dorsal vertebrae. Sternum with a 

 greatly developed bird-like keel, but no anterior spine-like pro- 

 jection. Little lateral expansion of the sternal plate. The coracoid 

 articular facets overlap, and are prolonged on to the lateral surfaces 

 of the keel. Radial crest of the humerus spiral, and directed 

 distally. Humeral articulation with the ulna a compact hinge- 

 joint ; with the radius a well-developed trochlea. Radius much 

 smaller than the ulna, and extremely attenuated in the median 

 region of the shaft. Radius decussating the ulna, passing from a 

 ventral preaxial to a complete dorsal preaxial position. Head and 

 neck of femur terminal. 



III. Mechanism of the Settle and Joints, and Movements 

 oe the Limbs. 



The skull is beautifully adapted to combine strength with light- 

 ness. It is a mere framework of triangles, either in section, 

 laterally, or at the base. It is constructed entirely on the canti- 

 lever principle. One end of the cantilever carries the beak and the- 

 other the brain-case, with the fulcrum at the mandibular articulation. 

 The position of the teeth at the tip of the long jaws is mechan- 

 ically bad, as with the tension on the back of the skull, exerted 

 by the necessarily powerful neck-muscles, combined with the- 

 weight and strain of any large prey struggling in the jaws, the 

 beak would tend to break midway between the tip and the fulcrum. 

 To counteract this, the premaxillar bar is triangular and the maxillae- 

 are band-like, with the wide diameter vertical. These bones are- 



