384	THE EMPTY QUARTER
ammonoidea :
Erymnoceras spp.
lamellibeanohia :
Paralldodon sp.,
Mytilus jwensis Roemer,
Mytilus (Arcomytilus) cf. asper (J. Sowerby),
Mytilus (Phcvromytilus) plicatus (J. Sowerby),
Edigmus integer Douvill6,
Lopha cf. solitaria (J. de C. Sowerby),
Exogyra nana J. Sowerby,
Chlamys cf. fibrosa (J. Sowerby),
CUamys n. sp.,
Ceratomya excentrica (Roemer),
Ceratomya cf. paucilirata (Blanford),
Ceromyopsis cf, helvetica de Loriol,
Ceromyopsis cf. rostrata Douville,
Quenstedtia cf. mactroides (Agassiz),
Homomya inornata (J. de 0. Sowerby),
Pholadomya carindta Goldfuss,
Pholadomya aubryi Douville.
At Uwainidh, in the same neighbourhood, a well-preserved
specimen of the lamellibranch Lopha fiastellata, (Schlotheim) was
found. Specimens collected at Riyadh itself show that the town
is underlain by Jurassic limestones similar to those of Haisiya.
The fossils from Sha'ib Markh consist mainly of casts of a large
species of Nerinea (N. cf. desvoidyi d'Orbigny) preserved in a
yellowish-brown sandstone, but also include Homomya cf. inornata
(J. de C. Sowerby) and Mactromya (— Uniccvrdium) cf. globosa
Agassiz. It is interesting to note that the matrix of these speci-
mens is identical with that of the specimens of the same species
of Nerinea recorded from Bakkain in Newton's paper, and of the
brachiopods from Hamar recorded as Rhynchonella cf. subvariabilis
Davidson,
The Khashm Amur fossils occur partly in a sandstone some-
what lighter in colour than the Nerinea bed of Bakkain and Sha'ib
Markh, and partly in a light-coloured marly limestone. They
include the following species :
gastbopoda :
Nerinea cf. desvoidyi d'Orbigny.
lamellibbanchia :
Parallelodon sp.,	'         ,
Mu&vulus n. sp.,