B. B. Neidon — Fossils from Nubian Sandstone, Egypt. 397 



which these fossils were obtained, the lithological nature of the 

 matrix is identical in both areas, and may therefore be regarded as 

 of similar age, so that the fauna of the Jowikol Beds exhibiting fresh- 

 water and marine characters is consequently of estuarine origin, and, 

 moreover, may be determined as of Senonian horizon. 



EXPLANATION OF PLATES. 

 Plate XIX. 



Topographical sketch-map of Egypt, showing localities of Nubian Sandstone Fossils, 

 from the original designed by Dr. John Ball (see ante, p. 353). 



Plate XX. 

 Unio Humei, sp. nov. 



FIG. 



1. Left lateral view of specimen. 



Unio Ckosthwaitei, sp. nov. 



2. Left lateral aspect. 



3. Dorsal view of same, showing ligament and eroded umbones. 



4. Younger form of probably the same species, associated with Mutela mycetopoides. 

 4«. An enlarged view of the same specimen, x \\. 



0. Dorsal view of another specimen with ligament, and valves slightly open at 

 the ends. 



6. Surface structure of same, showing concentric lineations, sometimes bifurcating, 



and transverse ridgmg. x 4. 



Unio Jowikolensis, sp. nov. 



7. Right lateral view of specimen, with adherent Annelid tubes. 



8. Surface structure of same, showing irregular lineations with transverse ridges 



between, x 4. 



9. Smaller specimen of the same species, left lateral aspect. 



10. Dorsal view of same, showing eroded umbones. 



Mutela mycetopoides, sp. nov. 



11. Right lateral aspect of specimen on matrix, associated with a probably young 



form of Unio Crosthxcaitci. 



12. Magnified view of surface structure in the postero-dorsal region, x 4. 



Galeolakia riLiFORMis, J. de C. Sowerby. 



13. Portion of the colony adherent to the valve of XJnio Jowiholemis. x 4. 



The above specimens were obtained from Jowikol, on the east bank of the Nile, 

 between Kalabsha and Aswan. 



Plate XXI. 

 Inoceramus Balli, sp. nov. 



1. Left lateral view of specimen slightly reduced in size, x f . Showing the 



prominent costtc and compressed regions. 



2. Dorsal view of same, exhibiting the elevated and arched character of the umbonal 



region and its inclination posteriorly, x f . 



3. Surface structure, showing the fine lineations on the costfe and grooves — a restored 



figui-e. X y. 



This specimen was from the west end of the Aswan Dam. 



Note. — Unless mentioned to the contrary, the figures on Plates XX and XXI are 

 represented of the natural size. The specimens belong to the Museum of the 

 Geological Survey of Egypt. 



