414 



That this bone is really the homologue of the hyomandibular and 

 symplectic in the fish, becomes, I think, still more clear when we 

 compare it with such an aberrant form of piscine suspensorium as 

 is presented by some of the eel-tribe (Murcena, e.g.). In these fishes 

 the suspensorium is formed by only two bones, a small distal quadra- 

 turn, which, as usual, articulates with the lower jaw, and a large wide 

 proximal bone, which articulates above with the post-frontal and 

 squamosal, gives attachment to the operculum and to the cornu of the 

 hyoid, and sends down a process towards the articular head of the 

 quadratum. The single bone, which represents the three pterygoids 

 of other fishes, is articulated for the most part with the quadratum, 

 but partly with this proximal bone. The latter, therefore, clearly 

 represents both the hyomandibular and the symplectic bones of 

 ordinary fishes. 



But if the suspensorium of Triton be compared with that of 

 Murcena, e. g., it will, I think, be hardly doubted, that while the 

 distal ossification in the former corresponds with the quadratum, 

 the proximal answers (at any rate, chiefly) to the hyomandibular 

 bone of the Murcena. Indeed it differs from the latter principally in 

 being an ossific deposit in the outer portion only of the primitive 

 cartilage*. 



Thus it would seem, that in the manner in which the lower jaw is 

 connected with the cranium, Pisces and Amphibia, as in so many other 

 particulars, agree with one another, and differ from Reptilia and 

 Aces on the one hand, as much as they do from Mammalia on the 

 other. And the difference consists mainly, as might be anticipated, 

 in the large development in the branchiate Vertebrata of a structure 

 which aborts in the abranchiate classes. A most interesting series of 

 modifications, all tending to approximate the ramus of the mandible 

 more closely to the skull t, is observable as we pass from the fish to 

 the mammal. In the first, the two are separated by the hyoman- 

 dibular, the quadrate, and the articular elements, the first of which 



* In Murtena Helena the suspensorium forms an obtuse angle with the axis 

 of the skull, though not so obtuse as in the frog. A strong ligament connects 

 the outer side of the distal end of the quadratum with the maxillary bone, 

 passing outside the lower jaw. If the posterior end of the ligament were ossi- 

 fied, it would correspond very nearly with the " quadratojugal" of the frog. 



f Of course in a morphological sense. Whether they are more or less distant in 

 actual space, is not the question. 



