Jurassic Fauna from Central Arabia. 393 
Lopha(?) philby?, sp.n. (PI. XI. figs. 2, 3.) 
Description. Shell of subtriangular contour, with a well- 
excavated inner margin; lower valve deep, robust, orna- 
mented with three or four principal radial costze, from which 
proceed further costee both by bifurcation and trifurcation, 
the inner marginal costation being of wide convexity and 
- separated from the others by a very deep and broad furrow 
resembling a lobe. The coste are prominent, swollen, and 
divided by moderately deep furrows, while the whole surface 
is of lamellose structure. ‘The interior exhibits a triangular 
ligamental area and a fairly large reniform muscular impres- 
sion, which is closer to the inner than the outer margin and 
not far from the basal line. Only a mere isolated fragment 
of the presumably upper valve is present in the collection, 
showing a partial internal view, the outer surface being 
buried in an intensely hard matrix, thus hiding up external 
features. This fragment seems to indicate that the upper 
valve was of flattened character, and might have had some 
radial ribs, which would suggest that the oyster belonged to 
Bolten’s genus Lopha, which is equivalent to Fischer de 
Waldheim’s Alectryonia of a later date. ‘There are several 
fragmentary examples of this shell in a reddish-brown siliceo- 
calcareous limestone with minute, rounded, ferruginous 
grains, It shows a resemblance to Cretaceous forms such as 
Ostrea devillei, Coquand, from France, and to Blanckenhorn’s 
Q. dienert from the Cenomanian of Syria; but neither of 
those species, however, is furnished with what may be 
termed the inner costal lobe, which distinguishes the present 
shell. 
Dimensions. 
Largest lower valve: mm, 
RGA PE ert cand o.5, eit chai t 45 
Bp ti ioth ad sas ee cca etn 50 
Dharetey 5 cae dh Seve ie qe 25 
Locality, Hamar. 
Lopha solitaria (J. de C. Sowerby). 
(Pl. XI. figs. 4, 5.) 
Ostrea solitaria, J. de C. Sowerby, Min. Conch. 1824, vol. v. pl. 468. 
figs. 1, p. 105. 
It is interesting to be able to recognize so well-known a 
European species as Lopha solitaria among the Arabian 
fossils, The specimen consists of a well-preserved upper 
