292 DE. C. W. A>'DEEWS OX A XETT PLESIOSArE [vol. IxXTiii, 



foramen often seen between the coraeoids in tins position, ^ 

 Posteriorly the coraeoids widen little, but do not seem to have 

 been produced outwards into postero-lateral processes. In front of 

 the surface for the scapula the shar2D border of the bone describes 

 nearly a semicircle, of which the anterior end forms the somewhat 

 inwardly projecting angle of the long narrow anterior prolongations 

 of the bone. The s^inphysial union seems to have been continued 

 to the slightly- expanded anterior end of these prolongations. There 

 is no emlence that there was any anterior union of the median 

 processes with the scapulae, but there probably was one with the 

 posterior processes of the clavicles. 



The scapula (sc.) is much thickened at its posterior end where 

 it bears the surface for union ^vith the coracoid, and also that 

 forming the upper third of the glenoid surface. These two surfaces 

 m.eet at an ano-le of about 95^. In front of this thickening^ the 

 ventral ramus of the bone first narrows, and then widens out into a 

 broad plate ; the outer border of this is straight, the inner concave, 

 the antero-internal angle being produced inwards to a rounded 

 point, which however did not reach the anterior prolongation of 

 the coracoid or the corresponding expansion of the opposite scapula, 

 as happens in the Elasmosauridse. There was consequently no 

 closed scapulo-coracoid fenestra. The venti*al face of the inferior 

 ramus of the scapula is concave, both from side to side and from 

 before backwards. The base of the dorsal ramus of the scapula 

 arises as a high plate of bone from the upper surface of the anterior 

 two-thirds of the ventral i-amus, into which it passes by a gentle 

 curve on its outer side ; while on the inner the curve is much 

 sharper, especially towards the anterior end, the shelf-like surface 

 thus formed supporting the similarly curved outer end of the 

 clavicle which fits closely against it. The upper limb of the 

 dorsal ramus forms a narrow backwardly dii'ected blade of bone, 

 narrowing towards its upper end : its upper edge is thin and sharp, 

 the lower somewhat thickened and rounded. 



The interclavicle {i.cl.) is a transversely elongated plate of 

 bone, the upper surface of which is gently concave, as also is its 

 anterior border. It is widest in the middle line, and terminates 

 laterally in blunt points. Its postero-lateral borders interlock with 

 the anterior borders of the clavicles in a close suture : there may 

 have been a notch or foramen in the interclavicle near its hinder 

 end, at. or a little in front of, the point where the claA"icles meet, 

 but the bone is incomplete in this region. Such a foramen is seen 

 in the clavicular arcli (B.M. R. 1322) of a Liassic Plesiosaur 

 referred by Lydekker to Thaumatosanrus megacephcdus^ (see 

 text-figure, p. 295). 



The clavicles (cZ.) are rather large bones, the form of which 

 is shown in the figure. Theii' anterior borders interlock with the 



^ For instance, in Cryptocleidus -. see C. W. Andre^vs, Cat. Marine Eept. 

 Oxford Clay (Brit. Mus.) pt. i, 1910. p. 180, where it is suggested that it 

 probably transmitted a blood-vessel. 



- This is referred below to the new genus Eurycleidus. 



