On Fossil Evidences of a Sirenian Mammal ( Eotherium ægyptiacum , Owen) from the Nummulitic Eocene of the Mokattam Cliffs, near Cairo

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Abstract
T he evidence of the Sirenian mammal now submitted to the Society is from the white, compact, fine-grained, calcareous stone of the Nummulitic Eocene Tertiary period, now quarried extensively in the Mokattam cliffs, south of Cairo, for the buildings in progress in the modern part of that city. The block of stone containing the fossil was shown and afterwards presented to me by Dr. Grant, an eminent practitioner in Cairo, who possesses a good illustrative collection of fossil shells from the above formation; but the appearances of the exposed parts of the present fossil were, as may well be supposed, both new and strange. That the block contained the cast of some organic cavity was the best interpretation I could, at first sight, offer; and the subsequent clearing away of the matrix determined the fossil to be part of the cranium, with a cast of its interior representing the brain, of a species of Sirenian mammal. The portions of the skull preserved are scanty; they include parts of the basioccipital, basisphenoid, and petrosals. The bodies of the two cranial vertebræ have not coalesced, but show the flat, vertical, roughish syndesmotic surface, which long remains in the recent Dugongs and Manatees †. The alisphenoids are confluent with the basisphenoid; and the line of union is impressed, on the inner or cranial surface, by the large trigeminal nerve. These portions of cranial bones have the dense texture characteristic of the Sirenian skeleton. The petrosals, of a deeper tint, show an almost crystalline fracture

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