in Ichthyo sauna and Sauropterygia. 



241 



Unless I have greatly failed to grasp his meaning, Professor H. G. 

 Seeley grounds his idea of the presence of a cartilaginous precoracoid 

 in Nothosaurus on the characters of the terminal border of the process 

 marked x, and on that of the part of the scapula marked x (fig. 3), and 

 also in the presence of the notch n, at the outer side of the process a*, 

 which he identifies with the notch in the anterior border of the Ichthyo- 

 saurian coracoid, and so with the precoracoid foramen (cor. for. of most 

 authors) in Reptilia squamata. Were the notch n converted into a 

 foramen by a cartilaginous band joining x and x, such cartilaginous 

 bar with the bony process x would constitute the precoracoid element 

 conceived by Professor H. Gr. Seeley. This hypothesis is not free 

 from difficulty. In both the primary divisions of Amphibia the car- 

 tilaginous precoracoid is more in line with the scapula, forming, as 

 it were, a ventral extension of this, than it is with the precoracoid, 

 and when the precoracoid ossifies (Urodela) in common with either 

 of the other components of the girdle, ossification appears to overrun 

 it from the scapula rather than to extend into it from the coracoid. 

 But in Nothosaurus, on the supposition that the process x is part of 

 the precoracoid, obviously, ossification has spread into this from the 

 coracoid and not from the scapula, with which also it has no com- 

 munity of direction. Next, as regards the supposed identity of the 

 notch w, at the outer side of the prpcess x, with the foramen of nerve- 

 passage in the Lacertilian coracoid. This in all lizards I have examined 

 with particular reference to its position is situated behind and usually 

 slightly towards the mesial side of the precoracoid tract or process, so 

 that the homologous notch in the Nothosaurian girdle is to be sought 

 at x"j and not at the outer side of x. 



cor for. 



Cor. 



FKJ. 4. Left half of shoulder girdle of Iguana tulerculata. 



But if we were to concede to Professor H. Gr. Seeley the presence 

 of a^re-coracoid in the Nothosaurian shoulder girdle joining x and a?', 

 its relation to the coracoid would be different to that which he assigns 



u 2 



