122 
PECTEN quinquecostata. 
TAB. LVI.—Figs. 4, 5, 6, 7, and 8. 
Spec. Cuar. Subtriangular, rather obligue, front 
semicircular, toothed ; convex valves gibbous, 
ribbed, principal costa six, with four lesser 
ones between each: surface finely transversely 
striated. Upper valve flat-toothed. 
ee 
Tue obliquity of this shell is slight, the length not muck 
greater than the width; the lines of growth frequently 
being deep and crossed by the ribs give the shell a fringed 
or furbellowed aspect: the flat valve has diverging striz 
and notches corresponding in number with the costa upon 
the hollow valve. The whole surface is covered with 
minute transverse striae, which in the chalk specimens are 
often nearly obliterated. Figs. 4 and 5 are from the Sussex 
Chalk near Lewes, by favour of G. A. Mantell, Esq. they 
very much accord with those of the green sand from 
Wiltshire, figured below, but appear to be longer, and to 
have the transverse striz of growth very remarkable. The 
shell represented at Fig. 5 is a curiosity, showing the inner 
side of the flat valve, which is slightly convex within. 
I gathered the small shell, Fig. 6, at Chute Farm, it is a 
young deep undervalve, with the transverse striz of growth 
neatly arching between the larger six coste. Figs. 7 and 8 
show the upper and under valves of different specimens, they 
are from the green sand at Chute, and are chiefly siliceous; 
for the use of one I am indebted to Thomas Meade, Esq. 
