136 J. 8S. GARDNER ON BRITISH CRETACEOUS NUCULIDA. 
or beak-shaped anteriorly, with subcentral umbones, a moderately 
defined lunular region, and the inferior margin very slightly con- 
stricted. Its surface is deeply striated, except towards the ex- 
tremities, which are smooth. There is no nacreous layer, and it 
occasionally presents remains of colouring in the form of alternating 
pale brown and cream-coloured bands. 
D’Orbigny combines the species with Leda subrecurva, Phillips, 
from Speeton ; but they are certainly distinct. Michelin’s specimens 
were from the Gault, and the dimensions are stated at 16 mm. in 
length, while the longest I have met with in England do not exceed 
11 mm.; it is further characterized as compressed, with central 
umbones and indistinct lunule. 
Since, however, [have only come across, in French collections, 
specimens bearing this name which are in every respect identical with 
those of our own Gault, I think the description may be imaccurate. 
Pictet describes, as LZ. Neckeriana, a very similar but even larger shell, 
18 mm. long, from the Gault of the Perte-du-Rhéne, distinguishing it 
from Michelin’s described type chiefly by the more open umbones and 
greater depth of the valves, characters which agree more with the 
actual French and English specimens which I have seen. It is 
possible that these may be distinct. local varieties ; but I think it 
preferable at present to admit but one Gault species of the “Z. sub- 
recurva” type. 
It appears in lists of Cambridge fossils ; but I have only seen twe 
imperfect specimens belonging to Mr. Jesson, which might possibly 
be referred to it. Mr. Meyer has shown me imperfect specimens 
from East Shalford, which render it certain that it, or a similar 
Species, is present in the Perna-bed there; and some casts from 
Speeton in different collections approximate very closely to it*. It 
ranges through the Lower Gault of Folkestone, and is rarer than 
the other species. 
Blackdown species. 
Lzepa tivgata, Sby., sp., in Fitton, Trans. Geol. Soc. 2nd ser. vol. iv. 
p- 342, pl. xvii. fig. 9 (1836). Plate IV. figs. 13-16. 
This species strongly resembles LZ. subrecurva, but is more elongate 
at both extremities and thus skiff-shaped. The umbones are less 
central and the lines of growth continued over the entire shell. The 
lip is strongly crenated internally, a character I have not hitherto 
detected in L. subrecurva. Sowerby’s description of the shell makes 
it “elliptical, posterior extremity slightly truncated, with a short 
point at its upper angle; surface transversely striated, with lines 
straighter than the lines of growth, which they consequently cross 
twice.” Even with Sowerby’s original specimens before me, | am 
not able to detect the latter character, which would indeed form a 
very unusual ornamentation. In his most perfect specimen however 
the growth has been arrested at about midway, the inner region 
being marked off from the marginal region by a deep constriction 
* They are undistinguishable from it, and bear in the British Museum 
the MS. names JN, semiaperta and N. cordiformis. Pl. V. figs. 26-29. 
