XVII. On the the modifications of the first and second visceral arches, with especial reference to the homologies of the auditory ossicles

Abstract

An ample material of rare Elasmobranch forms, especially, Heptanchus, Hexanchus, Centrophorus, Myliobates , and Trygon , which I had collected during the last summer on the South Coast of Portugal, and several fresh specimens of Hatteria , have induced me to submit the question of the modifications of the two first visceral arches to a reconsideration. The homologies of the auditory ossicles have not hitherto been settled beyond dispute, and only recently this question has again been taken up by Albrecht, Dollo, Bauer, and Gradenigo. The most important of these latest contributions has been made by Albrecht, who, chiefly for theoretical reasons, advocates that the whole of the auditory chain in all the Amphibia and Amniota is homologous with the hyomandibula of the Fishes.