Subclass OSTRACODA Latreille, 1806
Order PODOCOPIDA Müller, 1894
Suborder PODOCOPINA Sars, 1866
Digmocythere cronini n. sp.
Figure 16 (1-5)

1994 Cyamocytheridea? sp. Elewa, p. 145, pl. 2, figs. 11-12.

Etymology. The species is named after Thomas Cronin, US Geological Survey, USA, who with Hamed Khalifa, Geology Department, Faculty of Science, Assiut University, Egypt, were the first authors to recognize this form.

Diagnosis. A species with elliptical shape, smooth carapace with a prominent projection just behind mid-length and rounded anterior and posterior margins.

Material. Fifty-four specimens are referred to the new species. The holotype (A 10132) and the paratypes (A 10133 to A 10185) are deposited at the Geological Museum of the Geology Department, Faculty of Science, Minia University in Elewa's personal collection.

Type locality and stratum. A section west of Beni Mazar city, bed no. 1, yellowish white limestone, the Maghagha Formation, middle Eocene.

A 10132 (Holotype) (Female)
A 10133 (Paratype) (Male)

Description. Carapace elliptical in lateral view, with a slight ventral convexity; dorsal margin straight to slightly convex; ventral margin convex, with a prominent projection just behind mid-length; antero-ventral margin slightly concave; postero-ventral margin straight to slightly convex; anterior margin rounded; posterior margin rounded. The right valve slightly overlaps the left valve, especially ventrally. Maximum height at mid-length. Surface smooth. In dorsal view, carapace elliptical, narrow; maximum width at mid-length. Internal characters were not observed.

Sexual dimorphism. Presumed female carapaces are wider and shorter than presumed male ones.

Remarks. The new species resembles a species described as belonging to an uncertain family and genus by Khalifa and Cronin (1979, p. 181, pl. 1, figs. 5-6) from Gebel El Sheikh Fadl east of Beni Mazar city. Unfortunately, all the previous and presently studied specimens are complete carapaces; as a result, the internal features could not be observed. However, the new species externally differs from Cyamocytheridea Oertli, 1956, in having a distinct projection just behind mid-length and acuminate anterior and posterior margins. The maximum width is at mid-length in the new species, while it is posteriorly in Cyamocytheridea. Therefore, this form should not be assigned to Cyamocytheridea. On the other hand, because the new species has almost the same external characters of the genus Digmocythere, it is placed under that genus until the internal characters become available from a new material. Unfortunately, the characters essential for assignment of species to Digmocythere are the internal features (particularly the hinge). Further, the validity of that genus is questionable because of several factors: 1) the genus was named by a worker who used only published descriptions, but without actual observation of any specimens of the species; 2) the essential character for assignment to Digmocythere, a crenulate anterior hinge element, occurs in closely related species that are assigned to other genera; and 3 ) the American species and the northern African species, all of which were apparently shallow-water taxa, were separated by the Atlantic Ocean during the Eocene, so it is not clear how they are genetically related. Only observation of the muscle scars and the hinge will give clues regarding the phylogenetic distance of these species.

Occurrence. The Maghagha Formation; the middle Eocene of a section west of Beni Mazar city, bed nos. 1-5 and top of bed no. 8.