BIVALVIA. 113. 
Tt was a small flat specimen, with neither the angularity of outline nor the elevated 
umbo of the recent Pacific shells. 
Nucuta tavicata, J. Sow. Crag Moll., vol. ii, p. 81, Tab. X, fig. 8, and var. calva. 
| Supplement, Tab. VIII, fig. 5 a, 6. 
Localities. Red Crag passim. 
Var. calva. Cor. Crag, Sutton and Orford. 
The Coralline Crag variety differs from the typical form found in the Red Crag of 
Walton Naze in being smaller and more decidedly truncated, without the projecting part 
of the margin at the shorter or siphonal side of the valve. I propose to distinguish it as 
a well-marked variety under the above name, ca/va. 
This variety much resembles an Oligocene shell represented by Dr. Speyer (‘ Die 
Ober Oligocinen Tertiar gebilde,’ p. 42, Tab. V, figs. 3—5), called WV. peregrina, Desh., 
which, judging from the figure, seems to be of a form somewhat intermediate between the 
Red and Cor. Crag shells, but I have not been able to procure a specimen of the German 
fossil for comparison. 
Nucuna Proxima, Say. Crag Moll, vol. u, p. 87, Tab. X, fig. 7 (as WV. ¢rigonula). 
Nucuna Proxima, Say. Journ. Acad. Nat. Sce., 2, p. 270, 1822. 
Localities. Cor. Crag, Sutton and near Orford. 
At the above reference I observed that WV. prowvima of the American authors was 
probably the same as the Crag shell ¢rigonula, and as I have seen no reason to alter that 
opinion it is only right, as the name prozima has priority to mine, that the shell should 
be here placed under that designation. 
Nocuna nitipa, G. Sow. Supplement, Tab. X, fig. 12.. 
Nucuta niripa, G. Sow. Conch. Illustr., Nucula, No. 29, fig. 20. 
= = Hanley. Thesaurus, p. 46, pl. 229, fig. 120. 
Localities. Cor. Crag, Sutton and near Orford. 
As the British conchologists seem to consider this shell to be a distinct species I 
have here followed their example, although at page 87 of vol. ii of the ‘Crag Mollusca * I 
considered it to be only a variety of ¢rigonula, and as my specimens correspond with the 
recent form I have had one figured. It is less tumid than /rigonula and has a smooth 
