PELONETJSTES. 55 



anterior or posterior surface, or on both. The sacral and caudal ribs are not certainly 

 known in P. philarchus, but in P. evansi some bones referred to this position are 

 described and figured (p. 74, text-fig. 29). 



Should er-qir die (text-figs. 21, 22). — The shoulder-girdle of Peloneustes, like that of 

 the other Pliosauridse, differs widely from the Elasmosaurian type which has been 

 described above (Part I. pp. 106-111). The constituent bones, though large, are 

 relatively thinner and more lightly constructed, and the scapulae, though their ventral 

 ramus is much expanded, do not appear to have met in the middle line, though they 

 may have touched the anterior prolongations of the coracoids. Of the clavicular arch, 

 all that is known to have been present is a median triangular bone, the interclavicle 

 (text-fig. 22), which seems to have been interposed between the inner ends of the 

 scapula?. The lightness and comparatively smaller degree of rigidity of the shoulder- 

 girdle in this form, is no doubt connected with the fact, that the hind limb is here the 

 larger and presumably the chief means of propulsion, the reverse being the case in the 

 Elasmosauridse. 



The coracoids (text-fig. 21, cor.) are large thin plates of bone, the form of which 

 will be best understood from the figure ; the two meet in a long median symphysis 

 {sym.), making an angle of about 90° with one another ; the surface of union is very 

 narrow except towards the front, where there is a crescent-shaped thickening, the 

 convex surface of which is on the visceral side of the bone, while the concavity is on 

 the outer (ventral) surface (see text-fig. 21, A, C, sym.) ; the thickening of the bone at 

 this level is continued out to the articular surfaces (glenoid cavity, g.c, and scapular 

 facet, scap.f.). The antero-internal angle of the bone is produced forwards as a tongue- 

 shaped process considerably in advance of the glenoid cavity ; it is uncertain whether 

 or not this anterior process was in contact with the ventral ramus of the scapula. The 

 surface for the scapula {scap.f.) makes an angle of about 70° with that of the glenoid 

 cavity. Behind the glenoid cavity the thin outer border of the bone is concave, while 

 the posterior border is evenly convex ; the postero-external angle is not produced into 

 a strong process, as is the case in Cryptocleidus, except perhaps in advanced ago. 



The scapula (text-fig. 21, scap.) is, as usual in the group, a triradiate bone ; the 

 posterior ramus bearing the surfaces for union with the coracoid (cor.f.) and for 

 the anterior part of the glenoid cavity {g.c), is triangular in section. The ventral 

 angle is continued forwards as the thin, sharp, outer edge of the ventral ramus {v. p.), 

 while the inner angle is continued into its posterior border ; the outer angle is 

 continuous with the posterior angle of the dorsal ramus {d.p.). This is directed 

 upwards aud curves a little backwards; in its upper portion the anterior and posterior 

 borders are nearly parallel ; the anterior edge is continued forwards as a sharp ridge 

 on the upper surface of the ventral ramus, reaching nearly to its anterior angle; the 

 upper end of the dorsal ramus seems to have been tipped with cartilage. The broad 

 ventral ramus is much expanded anteriorly, forming a thin plate of bone with a 



