Manchester Memoirs, Vol. Iv. ( 1 9 1 1 ), No. 1 1. 9 



The account of the h'mbs given above shews how 

 slight is the difference separating Microcleidus hojiialo- 

 spondylus and M. macrop terns. It would be quite impos- 

 sible to separate them on the evidence presented by any 

 individual bone, but the fortunate occurrence of several 

 good skeletons shews that they are certainly different. 



The limbs shew an advance on the type most 

 common in the Lower Lias in their much more extensive 

 ossification, and also in the fact that the radius and ulna 

 are of the same length ; in all the species from the Lower 

 Lias the radius is very considerably longer than the ulna 



{Fig- 3)- 



Only one Upper Liassic species has yet been described 

 which has limbs at all closely resembling those of our 

 genus : — Plesiosaurus Guilelnii luiperatoris, of which the 

 limbs strikingl}' resemble those of Microcleidus ; I believe 

 the two types to be very closely connected, and shall 

 discuss their relationship in a future paper when I describe 

 the skull o{ Microcleidus. 



