BIVALVIA. 135 
size, deeply impressed, and there is a distinct pedal one within and a little below it; the 
anal one large and remote; the umbones are rugose, and generally eroded. ‘The epidermis 
is visible on well-preserved specimens, which have also the connector entire, extending from 
the umbo about half the length of the shell. 
A large portion of the stratum in which these shells abound at Hordwell is a marly 
bed, but I obtained a few perfect specimens from a pure siliceous sand. 
5. UN1o sUBPARALLELA, Edwards, MS. Tab. XX, fig. 13, a, 0. 
Unio Drsuayesi1? Prestwich. Quart. Journ, Geol. Soc., 1854, p. 118. 
Spec. Char. U. testa elongata, sub-quadrangulata vel ovato-oblongd, levigald, depressa, 
valde inequilaterali ; pedi-regione brevi, rotundatd ; siphoni-regione longiore, subangulata 
vel oblique truncata ; umbonibus depressis ; marginibus ventrali et dorsali subparallelis. 
Shell transversely elongate, or ovately oblong, smooth, depressed, very inequilateral ; 
pedilateral margin rounded; siphonal region much the larger, slightly angulated or 
obliquely trunculated ; umbones depressed; dorsal and ventral margins nearly parallel ; 
ventral margin slightly incurved. 
Length, 2. inches ; height, ths of an inch. 
Localities. Peckham (2dwards), Counter Hill, Deptford (Prestwich). 
The specimen referred to U. Deshayesii by Mr. Prestwich most probably belongs to the 
same species as the one here figured, but “its mutilated condition would not permit of 
determination.” 
In comparing our present species with the U. Wateleti (olim U. Deshayesii), the 
differences appear too great to permit of their being united, and I have therefore adopted 
the MS. name that was attached to Mr. Edwards’s specimen. 
I am the more disposed to this separation, because I have not only the figures 
and description of the French shell in the valuable work by M. Deshayes, but there is also 
a specimen in the cabinet of Mr. Edwards, sent from France by the author of the species. 
A shell from the “ ‘Terrain de lignite” in the South of France has been figured and de- 
scribed by M. Matheron under the name of Unio galloprovincialis; ‘Cat. meth. et descr. des 
corps organ. foss. des Bouches du Rhone,’ p. 168, PI. 23, fig. 1, which appears from 
representation very closely to resemble our own, and when the specimens themselves can 
be compared, may probably be found to belong to the same species. ‘The only difference 
I can observe on comparing the figure is that the umbo of the French fossil is rather the 
more prominent of the two. 
