248 



EEPTILIA 



CLASS III 



Fio. 352. 



Scaphognathus crassirostris, Goldf. sp. Upper Jura ; Eichstädt, Bavaria. 

 D, Antorbital vacuity ; fr, Frontal ; ju, Jugal ; vw, Maxiila ; N, Narial opening ; 

 pvtx, Premaxilla ; qu, Quadrate. 



antorbital vacuity is present as in birds and Dinosaurs, and is either confluent 

 with the external nostril on each side, or separated from it by a narrow bar. 

 The supratemporal vacuity is small, entirely enclosed, and placed far back- 



wards. The lateral 

 temporal vacuity 

 appears as a narrow 

 slit behind the orbit, 

 extending downward 

 and forward, and 

 bounded posteriorly 

 by the quadrate. 

 The cranial roof is 

 formed by the un- 

 paired frontal and 

 the smaller parietals, 

 which are without 

 a foramen. At the 

 base of the skull is placed the single occipital condyle, by means of which 

 the head is carried approximately at right angles to the long axis of the neck. 

 Natural casts of the brain cavity prove it to have been remarkably bird- 

 like, though smaller in proportion to the size of the skull. It was entirely 

 roofed by the frontal plate, which sometimes extended as far forwards as the 

 anterior border of the orbits, and formed not only their upper, but also a part 

 of their posterior border. The orbit is separated from the lateral temporal 

 vacuity by a trifid post-frontal plate, one brauch of which joins the squamosal, 

 and forms at the same time the outer bar of the supratemporal vacuity. The 

 orbit is bounded anteriorly by slender processes of the jugal and prefrontal, 

 which meet each other half-way, both of these plates being small and 

 triangulär. The quadrate is a relatively long and narrow bar, united with the 

 squamosal above, and with a buttress of the pterygoid below. In the facial 

 region, which closely resembles that of birds, sutures are always difficult to 

 determine. The snout is pointed in front, or in some cases slightly rounded, 

 and is formed by the enlarged premaxillae, which constitute the greater part 

 of the Upper jaw. Teeth, when present, occur in single series at more or less 

 irregulär intervals along the margin of the jaws. They are invariably simple 

 and conical, and implanted in distinct sockets. In some genera the sharp 

 margins of the jaws are completely edentulous, and may have been sheathed 

 with a horny layer, as in birds. 



The mandibular rami are straight and elongate, and fused together at the 

 Symphysis. They are composed of the usual six elements, but the sutures 

 between the latter are seldom determinable. A coronoid process is lacking, 

 and the Suspensorium is sometimes inclined forwards at a considerable angle, 

 so that the articulation with the quadrate is placed underneath the orbits. 



The pedoral arch comprises merely a pair of long, narrow scapulae, and 

 equally long but somewhat stouter and imperforate coracoids, which articulate 

 with the large sternum by a synovial Joint. There is no clavicular arch, nor 

 any indication of precoracoid elements. The humerus is of moderate length, 

 much expanded proximally, and exhibits a deltoid crest. The axis of the 

 distal articular facette is approximately at right angles to that of the head of 

 the same bone. Kadius and ulna sometimes doubly exceed the length of the 



