572 H. H. SWINNERTON. 



may have articnlated with a lateral element in the cranium. 

 I have no doubt that this is the homologue of the pedicle in 

 Lepidosteus. 



In Osteoglossum, Bridge (95^ p. 309) describes a similar 

 condition^ but here it is a process of the paraspheuoid, which 

 supplies a surface of articulation for the process from the 

 metapterygoid. He regards it as a '^striking example of 

 parallelism in evolution." May it not^ however, be a case in 

 which the pedicle has been retained, whilst the basipterygoid 

 process has been lost and functionally replaced ? 



Whether this is so or not, the fact I'emains that the lowly 

 Teleosts and Araia bring- the bony fish type near to one 

 having a pedicular articulation. This leaves little doubt 

 that the condition found in Lepidosteus is not secondar}^, 

 as Bridge supposed, but primary ; and that in the ancestor 

 the quadrate cartilage was attached, not merely to the edge 

 of the ethmoid plate, but also to the posterior region of 

 the trabeculse somewhere between the exits for the second 

 and fifth nerves. 



Huxley's comparison between the subocular arch of the 

 frog and the hyosuspensorial apparatus of the Teleosts (58) 

 ou the one hand, find the cranio-facial skeleton of Petromyzon 

 (76) on the other, implied a resemblance between the latter 

 two, which, as pointed out by Pollard, he ceased to recognise 

 later. Nevertheless, this resemblance does exist, and in no 

 respect is this more clearly shown by Petromyzon than in the 

 fusion of the ai'ch, anteriorly with the ethmoid and pos- 

 teriorly with the trabeculse, between the exit of the optic 

 nerve and below that of the trigeminus (Parker, 83, p. 401). 

 Nor is continuity of substance to be regarded as an important 

 difference, for, as shown above, it exists between the palatine 

 andethmoid in the latest developmental stages of some Teleosts, 

 and has been also observed by Parker in his earlier stages of 

 Lepidosteus (82, p. 450). Moreover, in my Stage III, the 

 hyomandibular forms a continuum with the auditory capsule. 

 Again, in Myxine all these points are marked by the presence 

 of a different kind of cartilage from the rest. 



