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BIVALVIA. 73 
There is a single specimen only of this species in Mr. Edwards’s cabinet, and this 
unfortunately is not in very perfect condition, but the figure is faithful, though a little 
improved. Our shell strongly resembles the figure and description of the French fossil 
above referred to, and I think it may be safely considered as belonging to that species. 
A recent species has this name, but it is quite distinct. M. Deshayes says the fossil is 
entitled to priority. 
18. Mopiona tTenvistriata, Melleville. Tab. XIII, fig. 3. 
MopioLa TENUISTRIATA. Mellev. Mem. sur les Sab. Tert. Inf. du Bass. de Par. (Ann. des 
Sc. Géol., 1843), p. 39, pl. 2, figs. 17—19; and pl. 3, figs. 
9, 10. 
Spec. Char, M. testa ovato-ellipticd, tumidd, tenui, fragili, utroque pariter rotun- 
data, pedi-regione parvd; superficie omnino striatd, striis tenuissimis, radiantibus ; 
striis incrementi elevatis, decussatis. 
Shell ovately elliptical, tumid or deep, thin, and fragile, equally rounded at both 
extremities ; exterior wholly covered with striz; radiating lines fine and thin, decussated 
by elevated lines of growth. 
Length, ths of an inch. 
Locality. Barton (Ldwards). 
This elegant shell is very rare as a British fossil, and of extreme tenuity. M. Melle- 
ville gives two figures of his species, presenting considerable diversity of character. The 
British fossil corresponds more closely with his figures § and 10, pl. ui, both in the 
outline and ornament. Our shell has the umbo almost at the extremity, and very slightly 
projecting. ‘The fine, radiating strize are regularly cut by lines of growth, making the shell 
appear as if punctured or cancellated. 
19. Moptota? tusicona, S. Wood. Tab. XIII, fig. 12, a, 6. 
Spec. Char. M. testi subcylindraced, levigatd, tenui, valde inequilaterali ; maryinibus 
dorsali et ventrali subparallelis ; pedi-regione parva, rotundata ; siphoni-regione compressa. 
Shell subcylindrical, smooth and thin; dorsal and ventral margin nearly parallel ; very 
inequilateral ; pedal region small and rounded; siphonal region compressed. 
Length, 3ths of an inch; height, ith. 
Locality. Whetstone? ; 
In the museum in Jermyn Street is a specimen of the matrix of London Clay with 
several tubes of the Zeredo, and located with them are two or three individuals of a 
Modiola ?; these latter have apparently taken their abode in the hollow of the tubes. The 
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