60 MOLLUSCA FROM THE CRAG. 
4. Mopiota costutaTa, fisso. Tab. VIII, fig. 6. 
Moprouvs costuLatus. Risso. Hist. Nat. de ’Europ. Merid., t. iv, p. 324, pl. xi, fig. 165, 
1826, non bene. 
Mopiota costuLaTa. Phil. En. Moll. Sic., vol. i, p. 70, t. 5, fig. 11, 1836. 
— — Id. - - - vol. ii, p. 50, t. 15, fig. 10, 1844. 
o Peracnam. (Scacchi) sec. Phil. En. Moll. Sic., vol. ii, p. 51. 
— costunaATA. Webb and Bertholet. Nat. Hist. des Iles Canaries, p. 103, pl. 7, B 
figs. 23, 25, 1842. 
— — Jeffreys. An. Nat. Hist., vol. xix, p. 313. 
— cyLinDRoipEs. S. Wood. Catalogue, 1540. 
CRENELLA cosTULATA. orb. and Hanl. Hist. Brit. Moll., vol. ii, p. 205, pl. 45, fig. 1, 1849. 
Spec. Char. Testa minuté, oblonga, subcylindricd, anticé angustata et ultra apicem 
producta, medio levi ; in utroque latere costato-striatd. 
Shell small, oblong, subcylindrical, anterior side somewhat contracted, extending 
beyond the umbo, middle smooth, with large costated strize upon both sides. 
Longest diameter, 3ths of an inch. Shortest, 2ths. 
Locality. Cor. Crag, Sutton. 
Red Crag, Walton Naze. 
Only one specimen in my cabinet has been obtained from the older or Coralline 
Crag Formation; but in the Red Crag at Walton it does not appear to be at all scarce, 
at least a couple of dozen have fallen to my lot, and in them a considerable range in 
variation may be detected. 
Our shell appears to agree with the figure and description of JZ. costwlata, in the 
first vol. of Philippi, which that author, in his second volume, has assigned to another 
species: amongst my specimens also are forms corresponding with what he con- 
siders to be specifically distinct, and they are therefore both introduced among the 
synonyma, as I am unable to separate into two species those which are found in the 
Crag; if, however, there be in the recent shells characters sufficient to justify a 
specific distinction, both forms seem to have been present in the seas that deposited 
the Red Crag, but from what is exhibited in the fossils, they may be fairly included in 
one species. 
There can be no mistake in regarding this as distinct from either J/. discrepans 
or JZ. marmorata, from both of which it differs in being more cylindrical, with 
also a greater curvature in the ventral margin. It is an elegantly-formed shell, 
the anterior side slightly projects beyond the umbo, somewhat tumid, with a rounded 
angularity crossing the shell diagonally from the beaks to the posterior part of the 
ventral margin, the anterior side is rounded, and deeply striated or ridged with about 
ten or twelve small ribs; the middle is plain, or only marked by lines of growth, 
while the greater half of the shell on the posterior side is covered with strie in a 
radiating manner, these are so conspicuous at the margin as to produce somewhat 
large and distinct crenulations on the inner edge, most conspicuous a little behind the 
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