Observations on the Skull of the Fossil Porpoise Zarhachis

During the past ten years a rather large number of vertebrae and other portions of skeletons of cetaceans have been obtained from the Calvert Miocene formation of Maryland. Most of these specimens were obtained by digging into the Calvert Cliffs. During severe storms many tons of sandy clay are dislodged from the face of the cliff by the undercutting action of the incoming tide. Many specimens are destroyed in this manner and at the same time others are exposed. Worn vertebrae and fragments of bones are found at frequent intervals on the beach along the Calvert Cliffs after a storm. With the exception of the zygomatic processes and the condyles, the bones of the skull do not withstand being rolled about by the waves and are soon broken up. When remains of pelagic mammals are found undisturbed in the greenish sandy clay, they are usually well preserved. Complete skeletons of these mammals are rarely found, but broken ends of bones and portions of skulls are often found protruding from the face of the cliff. Norman H. Boss, to whom we are indebted for most of the specimens described in this and the preceding papers, 1 has been extremely fortunate in locating and collecting specimens of fossil porpoises. One of the skulls which he collected during the past year belongs to the Miocene porpoise, Zarhachis flagellator. Although incomplete, this skull supplies most of the structural details which were missing on the other specimen. The locality at which this skull was obtained is less than 2% miles south of the previous discovery. The only certainly known remains of ZarhacMs flagellator from the Atlantic coast province of North America belong to four individuals. One of these is the type specimen, a single anterior caudal vertebra; a fairly complete skeleton which was described in 1924 represents the second specimen; the third is the cranial portion of a skull hereinafter described and figured; and of the fourth the right periotic alone was collected.