and Clavicular Arch in Sauropterygia. 



131 



quently (' Geol. Soc. Quart. Journ.,' 1883, p. 135) a diagram of the 

 shoulder girdle in this genus was given by that author, which represents 

 the scapula and coracoid as meeting each other on the Elasmosaurian 

 plan ; but, unlike Elasmosaurians, tbe scapulae are divided from each 

 other on the visceral aspect by a long triangular interclavicle (named 

 episternum) which shows a mesial notch in front. I have not seen this 

 specimen, which is not assigned to any species, locality, or collection. 

 It would appear to show an intermediate condition between Plesiosaurs 

 and Elasmosaurs, but it is impossible for me at present to affirm this. 

 No specimen is known to me which shows that in Pliosanrus the 

 scapula and coracoid completely enclose the coracoid foramina. The 

 evidence is imperfect, but it leads to the conclusion that the shoulder 

 girdle was Plesiosaurian in plan. 



t 



PlO. 4. — Interclavicle, Pliosaurus philarchus. ant-mar, anterior border; c, a 

 lateral surface which may have been a clavicular attachment. 



Pliosaurus philarchus, on which the genus Peloneustes has been 

 founded (' Cat. Foss. Kept, and Amph.,' Part II), in form of the 

 scapula closely resembles Pliosaurian remains in the British Museum. 

 Their approximating margins are convex, and between those margins 

 Mr. Lydekker has inserted the interclavicle (termed omosternum), 



with Professor A. H. Green, P.R.S., without finding evidence of this entosternal part 

 of the skeleton. What appear to be scapulae of Pliosaurus brachydeirus have the 

 inner and outer borders of the bones sub-parallel, with the anterior extremity but 

 slightly widened. Zittel has interchanged the names to Owen's figures of the 

 shoulder girdles of Pliosaurus and Plesiosaurus. I have not seen the originals of 

 those figures. 



