242 MESSES. HANCOCK AND HOWSE 



in von Meyer's work, tab. IX. The hind limb is seven inches 

 and five-eighths in length ; consequently the former is one-third 

 shorter than the latter. In P. Huxleyi the fore limb is one inch 

 and seven-tenths in length, the hind limb two inches and three- 

 eighths long ; the former in this species is therefore considerably 

 more than two-thirds the length of the latter. 



In the new species, then, the limbs vary more in length than 

 they do in the old ones, the hind limb being considerably longer 

 in the former, in proportion to the fore limb, than is the case in 

 P. Speneri. 



The difference likewise is strongly marked in the proportions 

 of the humerus. On referring to von Meyer's tab. IX., above 

 quoted, the constricted part of the shaft of the humerus therein 

 figured measures three-eighths of an inch wide, while the distal 

 extremity is nine-eighths of an inch across : thus it appears that 

 the latter part is three times wider than the former. In P. Hux- 

 leyi the narrow part of the humerus is one -eighth of an inch 

 thick, and the distal extremity is two-eighths of an inch wide : 

 so here the disparity is only as two to one, but in P. Speneri it 

 is as three to one. It must be stated, too, that in the old species 

 the proximal end of the humerus is nearly as wide as the distal, 

 while in the new species it is only slightly enlarged. 



EXPLANATION OF PLATES VII., VIII. 



v PLATE VII. 



Slab of Mavl-slate from Midderidge, containing the vertebral column, etc., 

 of Proterosaurus Speneri, von Meyer. 



PLATE VIII. 



Slab of Marl-slate from Midderidge, containing the skeleton of Proterosaurvs 

 Huxleyi, sp. nov. , Hancock and Howse. 



