H. B. Neicton — Fossils from Nubian Sandstone, Egyj^t. 389 



Germany which shows a slight basal sinuation, but differing greatly 

 in other respects, such as in its contour lines, being of more equal 

 height throughout, and having relatively shorter valves. 



A further comparison with a Wealden species might also be made, 

 as, for instance, with the well-known Unto po7-reckis, found chiefly in 

 British localities and first described by J. de C. Sowerby,^ the type 

 being a transversely oval sandstone cast with fairly inflated valves, 

 but possessing no basal sinuation, the ventral margin curving distinctly 

 outwards. None of the Unionida^ of higher Cretaceous deposits appear 

 to be in any Avay related to the present specimen. 



Occurrence. — This fossil consists of a reddish-brown ironstone cast of 

 a left valve isolated from the matrix. At the posterior extremity is 

 a small portion of the opposing valve, but being somewhat obscure no 

 details of importance can be cited in connexion therewith, except as 

 illustrating complete compression of the valves in that area. An 

 attempt has been made to develop the cardinal region, but without 

 success. 



Unio Jowikolensis, sp. nov. (PL XX, Figs. 7-10.) 



Btscriptio)). — Shell (with closed valves) compressed, sub-oval; umbones anterior 

 and eroded ; dorsal margin horizontal, nearly parallel with ventral border ; anterior 

 region sloping from umbones, margins elliptically and moderately produced ; posterior 

 part obtusely ridged from umbones to postero-ventral corner, with prominent area 

 sloping to i-ounded marginal extremity ; lateral face sloping from umhonal region to 

 basal margin, which is nearly parallel with dorsal line ; sculpture showing nearly 

 equidistant, fine, elevated, closely arranged, concentric striations with intermittent 

 lineations. 



Dimensions. — Height 30, length 47, diameter 18 mm. 



Remarks. — The greater height and more compressed valves of this 

 species removes it completely from its companion form Unio Crosthvaitei, 

 although so far as ornamentation is concerned, and its possession of 

 an obtuse postero-umbonal ridge, there is no doubt that both are 

 allied species. This fossil presents a general resemblance to Utiio 

 3Ienkei of Koch & Dunker^ from the Hanoverian "Wealden, but 

 differs in its finer ornamentation and the possession of a narrower 

 and more produced anterior extremity. There is a second example 

 of this species, of smaller size and with anteriorly eroded umbones, 

 showing perhaps more y)lainly the postero-umbonal elevation and 

 the lunuloid cavity. It is in a fair state of preservation, with the 

 exception of the sculpture lines, which are not so distinct as in the 

 larger specimen. 



Occurrence. — The face of the right valve of the specimen described 

 is largely covered with the tubes of the Annelid [Galeolaria fiUformis), 

 especially in the posterior region, otherwise the surface structure of 

 the shell is well preserved. The left valve has been nearly all 

 eroded awaj', showing the red-ironstone matrix and its microscopically 

 fine pisolitic character. 



Unio Ckosthavaitei, sp. nov. (PL XX, Figs. 2-6.) 



Description. — Shell (with closed valves) sub-cylindrical, inflated ; umbones anterior ; 

 dorsal margin nearly horizontal, arching posteriorly ; ligament elevated, prominent, 

 rounded, moderately thick, tapering in rear ; anterior region short, no defined cavity 



' Mineral Conchology, 1828, vol. vi, p. 189, pi. Dxciv, fig. 1. 



"^ Beitrage norddeutschen Oolithgebildes Versteinernngen, 1837, p. 58, pi. vii, fig. 1. 



