REPTILES. 115 



the prae-scapular band. It is a broad ray, somewhat curved inwards above, and receiving the 

 supra-scapula at a right angle (fig. 8) ; its posterior border is thick, and its anterior border 

 sharp, like a knife ; its suture with the coracoid is curiously bent upwards in front of the glenoid 

 cavity. 



The coracoid of Psammosaurus (figs. 7 and 8, cr.) ''> of very great extent ; and from the 

 obliquity of the suture runs up in front of the scapula ; contrary to what occurs in the latter bone, 

 it has all the Lacertian fenestrate clefts. The upper fork of .the three into which the shaft-bone 

 is divided runs along one third of the prae-coracoid band (p. cr.) ; the middle fork, or meso- 

 coracoid (m. cr.), is much larger, whilst the main coracoid (cr.) is a broad axe-shaped plate, having 

 a thick semi-osseous edge. This endosteal cartilage is very broad where it forms the boundary of 

 the lower and upper coracoid fenestree (1. c. f., u. c. f.) and the broad end of the meso-coracoid : 

 it narrows as it turns suddenly round to become the prse-coracoid band (Plate X, figs. 7 and 8, 

 e. cr., p. cr.). 



The large ichthyic Shoulder-splints of the Cyclodonts are in strong contrast with the delicate 

 rods seen in the Varanians ; figs. 7 and 8, cl., show the rather sudden bend that the clavicle 

 takes backwards, and that its pointed upper end only reaches to the top of the scapular shaft ; and 

 fig. 8 shows that it does not meet its fellow below : altogether, the splint system has lost much 

 of its relative potency ; whilst the endo-skeletal parts are very large. All the splints are very dense 

 and polished, and the two clavicles and the lateral arms of the inter-clavicle (i. cl.) are almost 

 cylindrical ; but the longitudinal bar of the latter broadens where it underlies the Sternum, 

 gradually becoming attenuated again towards its blunt point (fig. 8). The anterior ray of the 

 inter-clavicle, instead of equalling the others, as in Trackydosaurus, is a mere bud ; and this cha- 

 racter, combined with the retral bend of the lateral arms, gives the slender but strong inter- 

 clavicle of this Varanian the form of an anchor. The long, lance-shaped, longitudinal bar of the 

 inter-clavicle does not reach the same transverse line as the articulation of the first thoracic 

 ribs. 



The Sternum (figs. 7 and 8, st.) of Psammosaurus, is an elegant, but scarcely symmetrical 

 rhomb or lozenge; its coraco-sternal regions are longer than its costal margins; and the right 

 coracoid groove and lower lip proceed further backwards than the left ; the outline of these lips 

 is sinuous. There is no primordial fissure or "fontanelle," but the internal osseous deposits are 

 distinct and symmetrical (fig. 8), a definite line of unchanged cartilage running along the middle. 

 The interspaces of the ribs are elegantly lunate, and only three pairs join the Sternum, as in 

 certain Birds, for instance, Tinamus robustus and Tigrisotna leucolophum. The first pair belongs 

 to the tenth vertebra, which leaves in front nine or one more cervical vertebrae than are found in the 

 Cyclodonts : this is another ornithic character in this Varanian. The third pair of thoracic ribs, 

 however, are connected, not with the broad part of the Sternum, but with an unossified pedicle at 

 its end : there is some constriction where the osseous matter of the Sternum ends, and also where the 

 bony matter of the cartilaginous rods, which run into these ribs, ceases. What these rods (x. st.) 

 are it is difficult, at first, to say ; for they answer, below, to the horns into which two pairs of 

 ribs run in the Iguana, and are to a certain extent homologous with the free " xiphisternals" 

 of the Stellio Lizard. If longitudinal fission had taken place in these evidently generalised rods, 

 then we should have had the counterpart of what is seen in Stellio ; if transverse segmentation 

 had occurred at a moderate distance from their termination in the Sternum, then there would 

 have been a third "meso-sternal" piece added to the large plate: this joint might have had its 



