BIVALVIA. 43 
not, probably, for the organ of attachment, and as in the recent species, their shells 
vary much in those characters, the secondary fossils were most likely of this genus. 
1. Lima Exixis, S. Wood. Tab. VII, fig. 6, a—c. 
Lima Extuis. S. Wood. Mag. Nat. Hist., New Series, vol. iii, p. 233, Sup., pl. 3, fig. 1, 
1839. 
— — S. Wood. Catalogue, 1840. 
_ — Morris. Cat. of Brit. Foss., p. 111, 1843. 
Spec. Char. Testa ovatd, valde obliquia, depressd, fragili, ewili, utroque latere hiante ; 
costato-striatd, striis 25-35 asperimis, undulatis ; cardinis obliqui area angustd ; auriculis 
minimis equalibus. 
Shell ovate, very oblique, somewhat depressed, slender, and fragile, gaping largely 
on both sides; striated or costated, striae 25-35, rough, irregular and unequal, 
cardinal area large, oblique ears, rather small and equal. 
Longitudinal diameter, 1} inch. Height, 1} inch. 
Locality. Cor. Crag, Ramsholt, Sudbourn. 
Red Crag, Walton Naze. 
This elegant shell does not appear to have been very scarce in the Coralline 
Crag Sea, having myself procured a dozen specimens, most of which were from one 
locality, Ramsholt ; it is also occasionally found in the more tranquilly deposited portion 
of the Red Crag at Walton Naze, but its fragility in proportion to size is against 
its preservation in that deposit, as even in the older formation, specimens are not often 
obtained in a perfect state. 
Messrs. Forbes and Hanley have introduced this fossil into their synonyma of 
L. hians, considering it only as a variety of that species, to which opinion I am not 
willing to assent as a marked and striking difference is presented by my fossils 
sufficient by the ordinary mode of valuation in specific distinction to justify a 
separation. It somewhat resembles ZL. zvf#ata, but is flatter and undeserving of that 
name, and a shell in the British Museum called Z. scabrel/a, approaches it in some 
respects, but that is also more inflated, and is probably a variety of the zflata; I 
have therefore retained it as distinct, being intermediate between the British and 
Mediterranean species, approaching rather nearer to the latter than to the former. 
It may be more particularly described thus: the form is irregularly ovate, 
very oblique, gaping on both sides, and covered with raised and slightly undulating 
costulated strive, these are rough or scabrous, at nearly regular distances, covering 
in some specimens the entire surface, but generally a small space is left naked 
on the anterior side; in JZ. Aians the strie are less regular, thicker on the 
posterior side, larger and more dissimilar on the anterior, in this they are rather 
more distant upon the posterior half; the comparative dimensions of this are very 
different, taking the height at 1} inch from the umbo to the ventral margin, the 
diameter in the opposite direction is equal to 14 inch, but in Acans the height is at 
ah, 
