388 R. B. Newton — Fossils from Nubian Sandstone, Egypt. 



are apparently highly specialized, although the present-day aspect of 

 Majorca seems to afford no clue to causes sufficiently powerful to 

 necessitate the peculiar modifications noted above. It is to be hoped 

 that a further and more detailed study of these remains may throw 

 more light on this interesting problem. 



My thanks are due to Dr. C. W. Andrews, F.R.S., for his valuable 

 assistance in comparing the above specimens with material in the 

 British Museum (Nat. Hist.). 



II. — On some Fossils from the Nubian Sandstone Series of Egypt. 



By E. BuLLEN Newton, F.G.S. 



(PLATES XX AND XXI.) 



{Concluded from the August Number, p. 359.) 



DESCRIPTION OF THE FOSSILS. 



Group PELECYPOLA. 



Family Unionidae. 



Genus UNIO, Retzius (Philipsson). 



Dissertatio Historico-Naturalis Nova Testaceorum Genera, 1788, p. 16. 



Type = Mya margaritifera, Linnfeus. 



Synonyms — 



Margaritana, Schumacher : Essai d'un nouveau Systeme des Habitations des 

 Vers Testaces, 1817, p. 123, pi. x, fig. 4. Type = Margaritana fluviatilis, 

 Schumacher — Mya margaritifera, Liuna;us. 

 Alasmidonta, Say: Journ. Acad. Nat. Sci. Philadelphia, 1818, vol. i, p. 4.59» 

 Type = Unio undulata, Say. 



Unio Humei, sp. nov. (PI. XX, Fig. 1.) 



Description. — Specimen consisting of the natural cast of a left valve : form oblong, 

 subtrigonal, mostly compressed ; umbo anterior, depressed, incurved, succeeded in 

 front by prominent lunuloid cavity ; dorsal margin posteriorly elongate, oblique, 

 continuous with the terminal curvature of margin ; anterior region short, deep, 

 slightly inflated on the ventral side of umbonal area ; outer margin deeply excavated 

 beneath the umbo, afterwards of oval contour ; ventral margin anteriorly inflated, 

 deeply sinuated in rear ; posterior region furnished with an obtuse ridge dii'ected 

 obliquely from the umbo to the postero-ventral angle, on each side of which the valve 

 slopes and becomes compressed ; lateral face of valve between the anterior inflation 

 and posterior ridge triangularly depressed ; sculptm-e lines obscure. 



Dimensions. — Height 35, length 75, diameter 12 mm. 



Remarks. — This fossil, although mostly a cast, shows in places 

 certain evidences of shell markings, but which are much too obscure 

 for proper definition ; rough lines of growth can also be traced. Its 

 chief characteristics concern the presence of a lunulate area, the great 

 depth of the anterior region being about IJ times that of the posterior 

 end, and the extensive, somewhat trigonal depression on the lateral 

 face of the valve bordered below by the deeply sinuated margin. 

 There are few forms of fossil TJnionidfe which will bear comparison 

 with the Egyptian specimen, although at first sight its affinities might 

 be looked for among Wealden species. Messrs. Koch & Dunker ^ 

 have described Unio Menkei from the Wealden deposits of Xorthern 



1 Beitrdge norddeutschen Oolithgebildes Versteineningen, 1837, p. 58, pi. vii, fig. 1. 



