290 
PROFESSOE, H. G. SEELEY ON THE STRUCTURE, ORGANIZATION, 
forms the larger part of the bone, and it is only on the posterior aspect of the skull 
that what appears to be the small quadrate is seen, taking part with the squamosal 
in forming the articulation. Another step in the evidence of transition is needed, but 
I cannot doubt that when once a direct articulation is established between the lower 
jaw and the squamosal, with the articulation moved a little forward, and the small 
quadrate seen only behind, that the loss of work would lead to a diminished growth 
of that bone ; and that no function is eventually left to the quadrate but to support 
the tympanic membrane and surround the auditory aperture. Albrecht, tinding that 
occasionally a suture separates the articular part of the squamosal bone from the 
squamous portion in mammals, concludes that the zygomatic portion of that bone 
represents the quadrate bone, but, as we have seen that the squamosal in Anomodonts 
has the same relation to the skull, and to the lower jaw, as in Mammals, this interpre¬ 
tation has no support in the Anomodontia. 
Chimcera. 
Showing the relation of the centrnm to elements of the nenral arch in Elasmobranch Fishes, after Hasse. 
Professor Cope has described the quadrate bone of Clepsydrops natalis as having a 
horizontal ramus, which he affirms to be “ nothing more than the zygomatic process 
of the squamosal bone of the Mammalia forming with the malar bone the zygomatic 
arch,” But, from the fact that in the Dicynodontia and Theriodontia the squamosal 
bone always takes the development and function here attributed by Cope to the 
quadrate, there is an a p)'^dori improbability that a type so nearly allied to the 
Anomodontia should present a fundamentally different structure, when the external 
characters are described as similar. It is difficult to suppose there has been any error 
in the interpretation of the facts, since Professor Cope, in 1870, recognized the 
quadrate bone in a South African Anomodont skull ; but in the absence of fio-ures it 
is impossible to judge of the evidence on which the interpretation rests. 
A feature which specially distinguishes the Dicynodont skull from the skulls of 
allied animals is the enormous development of the squamosal bone, and, although 
it is difficult to speak with confidence on a matter that is necessarily hypothetical, it 
