J. S. GARDNER ON BRITISH CRETACEOUS NUCULIDA. 127 
striction, and more curved inferior margin. D’Orbigny remarks 
that it is related in form to WV. ovata, but that itis distinguishable by 
its better-marked and smaller lunule and by a different form of cast. 
One of Mr. Meyer’s specimens, and others in the Woodwardian 
Museum, show that the difference in the lunule is correctly noted ; 
but there are no British casts to compare in other respects. It is 
by no means an uncommon fossil in the Speeton Clay. 
Of two specimens figured (PI. V. figs. 2, 3) from the Leckenby 
collection in the Woodwardian Museum from this deposit, one 
ereatly exceeds the ordinary dimensions, measuring 27 mm. in 
length by 19 mm. in depth; this is the WV. ovata of Phillips, from 
the Speeton Clay, figured in the ‘ Geology of Yorkshire.’ 
Mr. Meyer has two specimens from the ‘ Perna-Bed’ of Redcliff, 
Isle of Wight, and one from the same horizon, from Kast Shalford. 
Those in the British Museum and at Cambridge are from the 
‘Cracker rocks’ of Atherfield, and the Speeton Clay. D’Orbigny 
describes it under Sowerby’s name J. obtusa, Terr. Crét. vol. ii. 
p. 163, and figures it as NV. planata, pl. 300, figs. 1-5. All 
references to NV. wmpressa and N. obtusa from the Neocomian or Lower 
Greensand should probably be read as NV. planata, the two former 
species being apparently confined in England to the Blackdown 
Beds. 
Gault Species. 
Novcuna carpsm#rormis, Michelin. Plate III. figs. 4-5. 
Nucula capseformis, Michelin, Mém. de la Soc. Géol. vol. m1. 
pl. 12, fig. 8 (1836). (WV. ovata, @Orb. 0. c. ante, N. de Rance, 
Price, Quart. Journ. Geol. Soc. vol. xxx. p. 358.) 
The outline is very similar to that of N. ovata, but the shell is 
more compressed, and of larger dimensions. J have not come across 
any British specimens quite equalling the length, 35 mm., men- 
tioned by D’Orbigny. The test is very thick, but has not the white 
and glossy appearance of NV. ovata, owing its appearance to the 
relatively thin covering of the nacreous layer. The striz of growth 
seem more regular, and there appears to be a far less tendency to form 
those deep furrows parallel with the ventral margin which are so 
characteristic in LV. ovata; but in all other respects their descrip- 
tions would be identical. It has never been met with in England, so 
far as I can learn, except at Folkestone, where it seems to be confined 
to the Lower Gault *. Itis relatively rare, and I have only been able 
to secure about 15 specimens. Its range in France is much greater, 
and among specimens from St. Florentin, a locality repeatedly 
referred to by D’Orbigny, there is a complete passage into the 
allied species VV. ovata. This may account for the confusion in 
regard to them that exists in D’Orbigny’s and in Pictet’s works, and 
it is not a little instructive to find species perfectly definable in our 
area, incapable of separation in another area so little removed. It 
* Tt is recorded by Price, /. ¢., only from the lowest and from the 11th 
‘ved ’ at Folkestone. 
