432 Mr. II. Day on the 



oblong facet of cartilage for articulating with the pedicle of. 

 the suspensorium." 



Swinnerton notes that Smith Woodward has discovered 

 that in Lepidotus there is a stout process of the metapterygoid 

 which bears a large facet which may have articulated with a 

 lateral element in the cranium. Swinnerton believes that 

 this process is the homologue of the pedicle of the palato- 

 quadrate bar in Lepidosteus. After a consideration of Smith 

 Woodward's description and figures (i o) it becomes difficult, 

 however, to suppose that the "lateral element in the 

 cranium," mentioned by him, can represent the basipterygoid 

 processes as in Lepidosteus, since in Lepidotus he figures 

 well-developed basipterygoid processes of the kf parasphenoid" 

 which apparently have sutural terminations, and therefore 

 could not have been apposed to the facet which is found on 

 the anterior process of the metapterygoid, though there can 

 be little doubt that these basipterygoid processes united with 

 the pterygoid region. 



Watson has shown that Megalichthys has similar processes 

 from the basisphenoid region of the basis cranii, and that 

 these have a sutural union with the pterygoid region, and 

 that Loxomma and Pteroplax also possess exactly similar 

 processes of the " basisphenoid " articulating with the same 

 region. In the present specimens the basipterygoid or 

 anterior lateral processes bear articulating faces, and, we may 

 take it, correspond with those of Lepidosteus, Lepidotus, and 

 Megalichthys amongst fishes, and with the similar processes 

 of the basisphenoid region as described by Watson in 

 Jjoxomma, Pteroplax, and Batrachiderpeton amongst the 

 fossil Amphibia, and in which the articulation is by facet 

 with the pterygoid region. 



It appears, then, that the additional pedicular articulation 

 of the palato-quadrate region with the trabecular is simply 

 continued in an homologous form in the union of pterygoid 

 region with the basipterygoid processes, a union by facet or 

 suture. 



Swinnerton notes that in the Selachii also there is a 

 constant recurrence of this pedicle of the palato-quadrate 

 region, pointing back to an ancestor " which certainly 

 possessed that feature." 



In that case, on the evidence brought forward above, we 

 have a line passing from the Selachii through the primitive 

 Teleostomes to the primitive Amphibia and Reptilia, on 

 which line there is this characteristic pedicular connexion 

 between the palato-quadrate region and the trabecular of the 

 chondrocranium, and hence these groups all agree in possess- 



