The cetacean remains, belonging to the genus _Zeuglodon_, were described by W. Dames,[48] who compared them with the American species _Z. macrospondylus_ and _Z. brachyspondylus_, but did not then consider them to represent a new species; in a later publication,[49] however, the same author described similar but more complete remains, also collected by Schweinfurth (from beds belonging to our Qasr el Sagha series), as a new species, _Z. Osiris_. A considerable number of fish-remains from Geziret el Qorn are also described in the earlier publication. Although the difference in size of the bones of separate individuals was considered by Dames to be sexual, it seems probable that there are two distinct species of _Zeuglodon_, as the smaller type appears to have a much greater upward range than the larger[50]; both species, _Z. Osiris_, and _Z. Isis_ occur in the Birket el Qurûn series, and a very fine mandible of the larger was obtained from these beds in the cliffs near the west end of the lake.[51] More recently a third species has been discovered by Stromer and described under the name of _Z. Zitteli_.[52] [Illustration: FIG. 4.—Profile of beds of Geziret el Qorn. 1. Hard brown sand-rock with large concretions of weathered globular sandstone on the summit; ferruginous nodular bands containing shell-casts occur near top. 2. Soft gypseous clays with bands of sand-rock and sandstone with _Ostrea_, _Cardium Schweinfurthi_, _Turritella_, corals, _Zeuglodon_, chelonian and fish-remains. 3. Brown sand-rock. 4. Soft gypseous clays and harder brown sandstones. 5. White shaly marl with fish-scales; hard band at top and soft sandy shaly clays below. The surface-slope is much less than shown in sketch and is generally covered by a deposit of lacustrine clays containing freshwater shells and fish-bones.] The accompanying profile (Fig. 4), measured during a hurried visit to the island for the purpose of correlating these beds with those of the mainland, shows the character of the lower beds of the Birket el Qurûn series at this point.[53] [Illustration: PLATE VII. WEATHERED CONCRETIONARY SANDSTONE (BIRKET EL QURUN SERIES) ON NORTH SHORE OF LAKE NEAR GEZIRET EL QORN.] The upper beds of the Birket el Qurûn series in this part of the Fayûm are lithologically similar to those just described, consisting of alternating clays and sandstones, about 37 metres thick. They are, however, generally much richer in fossil remains, which are likewise usually better preserved than in the lower beds. Some of the brown sandstones of this series are literally crowded with perfect examples of many of the typical mollusca; and further west, near the end of the lake, foraminiferal bands again become noticeable. Near Dimê the escarpment of these and the lower beds is gentle and inconspicuous, but followed westwards it becomes a bold precipitous cliff, increasing in height towards the western end of the lake, where it is capped by the lower beds of the Qasr el Sagha series.