Maticliester Memoirs, Vol. liv. (1909), ISio. 4 



IV. A Preliminary Note on two New Genera of 

 Upper Liassic Plesiosaurs. 



By D. M. S. Watson, B.Sc, 



Late Beyer Fellow of the Victoria University of Manchester. 

 Received and read November 2nd, igog. 



In 1876 J. F. Blake gave in Tate and Blake's 

 " Yorkshire Lias " a resume of our knowledge of the 

 reptilia of the Upper Lias known from Yorkshire. In it 

 he records two Crocodiles, eight Plesiosaurs, and three 

 Ichthyosaurs. No other Plesiosaurs have been described 

 since. 



Seven of these species are founded on more or less 

 complete skeletons, two of which I have been unable to 

 find 



The species are : — - 

 '^ Plesiosaurus" hovialospondylus, Owen. 



Founded on a complete skeleton in the British 

 Museum, which, however, shows neither girdle. Also 

 represented by a skeleton in the York Museum, and two 

 in the Manchester Museum ; this species is described 

 below, and made the type of the new genus Microcleidus. 



Plesiosaurus inacropterus, Seeley. 



Type specimen, a skeleton in the Sedgwick Museum, 

 Cambridge. Zone of D. commune, Lofthouse. 



This species requires re(iescription, but the specimen 

 gives no evidence of the structure of the girdles. 



December 22nd, igog. 



