146 MOLLUSCA FROM THE CRAG. 
are found in the same locality, and I have one specimen from the Red Crag in good 
preservation, exhibiting the same distinction. The figure by Nyst more strongly resem- 
bles this species than the last one, so also does that by Philippi. The latter author states 
his shell to be living in the Red Sea, thus giving a greater probability to its being 
different from the one living in the British Seas ; a few specimens of apparently the same 
species from the Older Tertiaries at Bracklesham are in the Cabinet of Mr. Edwards, 
one of which has been figured in Mr. Dixon’s work above referred to. In comparing 
them with the Crag specimens some trifling differences may be observed, but they 
do not appear of sufficient importance for specific distinction, and the Crag shell is in 
all probability the prolonged existence of the Bracklesham fossil. In dental characters 
they are precisely the same, but the Crag shell is rather more tumid, and it is also a little 
longer, the dorsal margin being somewhat less rounded than in the older shell, and the 
exteriors of the Crag specimens have merely fine and somewhat irregular lines of growth, 
while the Bracklesham fossil has rather more regular concentric striz, they however both 
present sufficient distinction to justify a separation from the recent British species. 
3. DipLoponTa? AsTARTEA, WVyst. Tab. XII, fig. 2, a, 6. 
TrLuina asrartEa. Nyst. Rech. Coq. Foss. d’Anv., p. 5, pl. 1, fig. 18, 1835. 
Lucina Gyrata. SS. Wood. Catalogue, 1840. 
— astartEa, Myst. Coq. Foss. de Belg., p. 121, pl. 6, fig. 4, 1844. 
Mys1a Americana? Conrad. Foss. Shells of the Med. Tert. United States, p. 30, pl.16, fig. 2. 
DirLoponTa PaRvULA? Nyst. Coq. Foss. de Belg., p. 139, pl. 7, fig. 2, 1844. 
Spec. Char, Testa obliqua, ovato-obiculari, depressiusculd, inequilaterali ; im senec- 
tute intus spissatd ; posticé majiore, anticée subangulatd ; dente cardinali bifido. 
Shell oblique, ovately orbicular, somewhat depressed, inequilateral, inside of 
specimens thickened; posterior side the larger, anterior subangulated: cardinal tooth 
bifid: no lunule. 
Diameter, 2ths of an inch. 
Locality. Cor. Crag, Sutton. Red Crag, Sutton. 
This shellis very abundant in the Red Crag, but it is rather scarce at one locality, 
from the Older Formaiton of the Coralline Crag, and presents some slight differences, 
though not sufficient to remove it from the species. 
Our shell measures three quarters of an inch from the anterior to the posterior 
side, and about the same or a trifle less from the umbo to the ventral margin, these 
proportions are occasionally reversed, but there is in general not much variation 
in this species: it is somewhat oblique, and measures rather more from the dorsal edge 
or position of the ligament to the opposite margin than ina contrary direction, although, 
in the young shell, it is the reverse; the umbones are prominent, the hinge has one simple 
and one bifid tooth in each valve, the surface is marked with somewhat irregular lines of 
growth at considerable distances. The interior in the adult shell is much thickened, 
