Development of the ShouIdet'ijirJle of a Plesiosaur . 333 



tlian ill /*. ucalcyon ; a streak in the cell along the median 

 m'lvure, below wliicli, between tlie second and tliird median 

 nervulcs, i.s a loii;^ angular-shaped cream-coloured spot, which 

 extends almost to the outer margin ; a cream-coloured spot 

 about the middle of the inner margin, and a long broad spot 

 joining it above the submedian nervure : secondaries golden 

 brown, crossed above the middle by a wide cream-coloured 

 band, which is much dentated on the out'ir edge; the inner 

 margin of the wing thickly clothed with orange-yellow hairs. 

 Underside : primaries very similar to the upperside, but paler 

 in colour ; secondaries paler than above, the veins all black, 

 the basal portion of the wing deep reddish brown, not crossed 

 by a light-coloured band, as in P. ucalcyon ; a large black 

 spot on the costal margin and a white dot at tne base. 

 Head, antenna3, and thorax black ; abdomen brown, with a 

 row of yellow spots on each side; legs black. 



Expanse 4 inciies. 



I lab. Upper Congo {Mas. Druce) . 



This species is allied to P. ucalcyon, Hewitson, and 

 P. auriger^ Butler, but very distinct from either. P. harpagon, 

 Grose Smith (Ann. & Mag. Nat. Hist. ser. 6, vol. v. p. 224), 

 is the same as Mr. Butler's species, and therefore will not 

 stand. 



XLII. — On the Development of the Shonlder-yirdle of a Plesio- 

 saur (Cryptoclidus oxoniensis, Phillips, sp.) from the 

 Oxford Clay. By C. W. ANDREWS, F.G.S., Assistant in 

 the British Museum (Natural History). 



'J'he structure of the pectoral girdle in the Plesiosauria has 

 been the subject of much controversy, and various conHicting 

 views as to the homologies of some of its parts are held. It 

 is not, however, necessary here to recapitulate these different 

 opinions, but for the present purj)ose it will be sufficient to 

 mention that the chief points in dispute are : — (1) The nature 

 of the anterior ventral bar of the scapula ; (2) the homology 

 of the anterior structure, which has been variously regarded 

 as omosternalia or as the clavicular arch. 



The abundant Plesiosaurian remains obtained by Mr. Leeds 

 from the Oxford Clay near Peterborough render it possible to 

 describe several stages in the growth ot an Elasmosaurian type 

 of pectoral arch, which seem to throw some light on the points 

 at issue. The species, to which the remains here described 

 belong, is the commonest of those found in the locality above 



Ann. tO Miig. iV. Hist. Ser. G. Vol. xv. 23 



