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BIVALVIA. 65 
This species much resembles M/. Bernayi, Desh. (An. sans Vert. du Bassin de Paris, 
t. 11, p. 13, Pl. 74, figs. 13—16), particularly in the outline, but it differs in having a 
smaller pedal region. Our shell is ornamented between the rays on the siphonal region 
with elevated ridges or regular lines of growth, decussating, as it were, the interspaces. 
Fig. 15 is the cast of a shell in the late Mr. Dixon’s collection of Eocene fossils in the 
British Museum ; unfortunately it is without a locality. It resembles in outline the above 
species. 
4. Mopioxa porsata, Morris. ‘Tab. XI, fig. 2. 
Mopiora porsata. Morris. Geol. Journ., vol. x, pt. i, p. 158, pl. 11, fig. 14, 1854. 
“ Ayare species. ‘The specimen is hardly sufficiently perfect for an exact determination 
of its characters. It differs from the preceding species (JZ. IZ/fchelli) in the umbo not 
being so terminal, and the form being less spathulate and more compressed.” (Jorris.) 
Locality. Sundridge (Prestwich). 
The only specimen that I have seen is the one figured, and I am unable to add to the 
description given by the proposer of the species. The prominent diagonal ridge is pro- 
bably accidental, but the pedal side is considerably extended, if it be natural and not 
forced out by pressure. 
5. Moprona rvecans, J. Sowerby. Tab. XII, fig. 5, a—c. 
Mop1o1a ELEGANS. J. Sow. Min. Conch., t. ix, left-hand figures. 
— — J. Morris. Catal. Brit. Foss., p. 211, 1854. 
Myritus eLecans. D’Orbigny. Prod. de Paléont., p. 391, 1850. 
Spec. Char. Testd tenui, ovato-clongatd vel subtrapezoidali, tumidd, subcarinald ; 
pedi-regione brevi, siphoni-regione rotunda; margine dorsali paulo angulato ; strirs 
utroque divaricatis, spatio mediano levigato ; margine ventrali subrecto, 
Shell thin, elongately ovate or subtrapezoidal, tumid, and obtusely keeled ; pedal region 
short and rounded; dorsal margin obtusely angulated or curved ; striae on both sides 
divergent, middle plain ; ventral margin slightly contracted ; shell nacreous. 
Length, 14 inch. ‘ 
Localities. a, Highgate (Wetherell), Bognor, Richmond Park (J. Sowerby), Clewer 
Green? (Prestwich); ec, Bracklesham, Barton (Hdwards) ; 6, Hordwell (Edwards). 
This appears to have extended from the lowest to the uppermost of the Eocene 
deposits ; it is not rare, and is subject to considerable variation. It is less pointed on the 
pedal side than JZ, /astata. Our shell is thin, and some specimens are so irregularly 
tumid as to form an obtuse keel or ridge from the umbo to the edge of the ventral margin 
of the siphonal region, but in others this is by no means prominent, as if this keel were 
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