V.— Observations on the Basilosaurus of Dr. Harlan ( Zeuglodon cetoides , Owen).

Abstract

Plates VII., VIII., and IX. In the recent discussion on the Stonesfield fossil jaws, one of the arguments adduced in support of the Saurian hypothesis of these jaws was founded on the presumed existence of a reptile possessing teeth with double fangs, this reptile being the Basilosaurus of Dr. Harlan*. I refused to admit the validity of this argument until the teeth had been subjected to a re-examination, with an especial view to their alleged mode of implantation, and I adduced as reasons for my objection, the instance of the Megatherium , in which the highest authority in Comparative Anatomy had been deceived in regard to this very point of structure. (See ante, p. 61.) But the appeal to the Basilosaurus had rendered it desirable to determine, not only the actual mode of implantation, but also the general conditions of the teeth of that interesting and problematical fossil, and I felt more especially desirous to apply to them a test founded on the microscopic examination of their intimate structure, which in many other cases I had found to afford very satisfactory and unexpected results. The arrival of Dr. Harlan in this country with some of the remains of the extinct animal in question, and the permission which he has liberally granted me of having the sections of his valuable fossils made which I required, have enabled me, much sooner than I could possibly have hoped, to arrive at such conclusions, as to the nature of the Basilosaurus , as can be safely