I 
129 
PECTEN sulcatus. 
TAB. CCCXCIII. —Fig. 1. 
Spec. Char. Obliquely orbicular, with 20 
obscurely tripartite rays, the intermediate 
spaces longitudinally striated, the whole 
rough with minute scales ; internally sul- 
cated; ears nearly equal. 
V alyes nearly equal, convex, shorter than wide, with 20 
rounding rays ; each ray is composed of about three scaly 
ridges, and between each ray are several lesser, but 
equally rough ridges , within are 20 furrows correspond- 
ing to the external rays ; the margin is toothed. 
A common Crag Fossil, generally known by the name 
of P. opercularis, although sufficiently distinct from the 
recent species so called ; the internal furrows are a con- 
spicuous character, besides which the striae upon the ribs 
are sufficient to distinguish them. There is a species 
from New South Wales more nearly allied, but in it the 
spaces between the rays are flat, and transversely 
striated, but not scaly. 
Very abundant in the loose Crag at Aldborough, but 
rather scarce in the more compact Crag of Sudbourn, 
and other parts of Suffolk. 
PECTEn"" gracilis. 
TAB. CCCXCIII.— 2. 
Spec. Char. Orbicular, thin, convex, with 
many small, longitudinal ridges ; concentri- 
cally striated ; striae close, elevated, sharp ; 
ears unequal ; margin entire. 
JLonger than wide, every fourth ridge is rather more 
elevated than the rest, and has an opposed grove within 
the valve, that is much more conspicuous than those, 
which, on account of the thinness of the shell, are 
formed by the other ridges ; the striae are pretty uniform 
over the surface, and not divided into scales, they are 
however strongest near the margin. 
Two specimens, but of the same valve found in the 
Crag near Ipswich, were formerly added to my cabinet 
of Fossils by Mrs. Cobbold, they are extremely fragile. 
