BIVALVIA. 69 
Spec. Char. M. testa elongato-ovatd, obliqud, incurvd, striata ; striis numerosis, radi- 
antibus, divaricatis, spatio mediano levigato ; pedi-regione brevi, margine rotundato, crenu- 
lato ; regione dorsali subarcuato. 
Shell elongately ovate, oblique, incurved, striated; strize numerous, radiating, and 
divaricating ; middle portion smooth; pedal region short, with rounded and crenulated 
margin ; hinge-line somewhat arched. 
Length, 2 inches. 
Localities. Brockenhurst (2dwards). 
Belgium, Hoesselt (/Vyst). 
This does not appear to be rare in England. 
I agree in opinion with M. Nyst, that this is quite distinct from Jf. hastata, Desh., 
but that it is the one so called by Goldfuss. Our shell agrees precisely with the Belgian 
fossil. This appears to be intermediate in form between JZ. elegans and M. hastata ; 
it has a greater curvature in the ventral region than that of the former, but less so than 
in the latter, and it attains to a greater magnitude than either. The rays multiply upon 
the older portion of the shell, having there double the number that there are upon the 
younger shell. The ventral region is free from rays, and the hinge appears to possess two 
or three teeth. These are wholly irrespective of the denticulated margin produced by the 
few coarse rays which cover the pedal region. 
12. Moprona Prestwicar, Morris. Tab. XIII, fig. 7. 
Mopro.a Prestwicurt. Morris. Mem. Geol. Surv., pp. 46, 147, t. 2, fig. 5, 1856. 
_ Nystrana. Forbes. Ut supra (name only). 
— — Morris. Catal. Brit. Foss., p. 211, 1854. 
Spee. Char. “ M. testa ovato-clongatd, angustd, subdepressd, supernée dilatatd, longitu- 
dinaliter striata ; striis numerosis obscuris, margine crenulato ?” 
“An ovate, elongate shell, of somewhat spathulate form, marked with numerous 
radiating but rather obscure stria.”’ (Morris.) 
Length, \ inch. 
Focality. Wempstead Chiff (Morris). 
The name of WVystiana was originally given to this species by the late Prof. U. Forbes, as 
written upon the plate above referred to. ‘There was, however, no description appended, 
and the specific name having been already used in this genus, the describer considered 
himself justified in revoking the one first imposed, and I have for the same reason fol- 
lowed his example. 
A mass of clay in Mr. Edwards’s cabinet, with a surface an inch and a half square, has 
not less than twelve specimens of various sizes upon it, with the exterior upwards, and it 
is somewhat singular they should all lie in that position ; they appear to be single valves. 
