184 MOLLUSCA FROM THE CRAG. 
Shell roundedly trigonal, slightly inequilateral, often somewhat oblique, and 
deformed; posterior side the broader or higher; dorsal margin rather rounded ; 
externally sulcated, or covered with numerous rounded ridges ; margin smooth. 
Diameter, ths of an inch. 
Localities. Red Crag, Sutton, Alderton, Bawdsey, Walton-on-the-Naze. 
Mam. Crag, Bridlington, Bramerton, Thorpe. 
Clyde Beds and Uddevalla. Recent, Britain, Scandinavia. 
This species is not’ by any means rare in the Red Crag, but the shell found there 
is generally that variety which has the lesser number of ridges, although amongst 
my specimens there is a variation from 30 to nearly 50. In the newer deposits of 
Bramerton and Bridlington the specimens are often nearly smooth, or have a greater 
number, and finer striae, while the shells also are often somewhat deformed, with a 
greater comparative length, and a more quadrate kind of outline, and the apices are a 
little eroded. 
What may be called the normal form (fig.8@) is subtrigonal, with a diameter as 
great from the umbo to the ventral margin as from the anterior to the posterior side, 
the umbo curving a little towards the anterior; the shell is generally somewhat 
compressed, and the ridges of the exterior are rounded and smooth, and about as 
broad as the spaces between them; the hinge is not very broad, and there is a 
somewhat prominent anterior lateral tooth at the extremity of a large and elongated 
lunule, and the dorsal margin is generally more or less rounded. The Red Crag 
furnishes specimens very variable in outline and somewhat deformed, but they are 
always regularly ridged and sulcated. 
The recent specimens do not often exceed half an inch in diameter, and have been 
obtained in ten as well as in eighty fathoms. 
11. ASTARTE CREBRILIRATA, S. Wood. Tab. XVI, fig. 2a—é. 
Spec. Char. Testa transversd, ovato-trigond, inequilaterali, tumidiusculd, crassa; posticé 
longiore, subtruncatd ; striatd, striis crebris obtusis confertis, lunuld elongata, eacavatd, 
margine crenulato. 
Shell transverse, ovately triangular, or wedge shaped, inequilateral, slightly tumid, 
thick ; posterior side the longer, and truncated, externally striated or ridged; strize 
numerous, close, rounded, and obtuse ; lunule elongated, deep ; margin crenulated. 
Length, ths of an inch; hezght, ths ditto. 
Localities, Red Crag, Sutton, Walton-on-the-Naze. 
Recent, Arctic Seas. 
A few specimens only of what appears to be a distinct species have been obtained 
by myself from the Red Crag. They correspond very closely, and in such a variable 
genus as this, may perhaps be considered as identical with a living species in the 
Cabinets of Messrs. Morris and Lowry, and said by those gentlemen to have been 
