178 Mr. H. Seeley on new and little-known Fossils 
Hinnites trilinearis (Seeley), var. 
An irregular shell, about 6 inches long and nearly as wide,which 
has the convex valve very moderately inflated, the other valve 
flat or coneave; so that the shell has a compressed aspect. In 
the young state it nearly resembled Cambridge examples of H. 
trilinearis in the aspect of the convex valve; but the ribs begin 
to disappear before the shell is half grown, so that the greater 
part of it is nearly smooth, being marked with the eccentric hnes 
of growth and faint prolongations of the mbs. The concave 
valve resembles the flat valve of H. trilinearis im having the ribs 
with which it is ornamented much more dense than on the large 
valve; they are rather more dense than in Cambridge speci- 
mens, and, instead of getting wider apart with age, get rather 
closer ; they extend to the margin of the shell. 
Hinnites Salteri (Seeley). 
Another large species of this genus is known by a convex valve 
of growth more regular than usual, measuring 4 inches in each 
diameter. Itis about as much inflated as the large valve of Pecten 
maximus, and ornamented by a large number of (about twenty-five) 
primary ribs, which radiate from the umbo, are little raised, and- 
sharp. Commonly between each two ribs there is another in 
the middle of the iniercostal space, much less elevated ; and on 
each side of this are frequently seen one or two tertiary ribs. The 
whole intercostal space is densely marked with fine radiating 
strie. H, trilinearis is the species to which it comes nearest. 
Perna sulcata (Sow.). 
Two distinct varieties occur—one the common typical form, the 
other that partly suleated shell cccurring in the Grés Vert, which 
in its young state is quite smooth. I suspect that the shell de- 
scribed from the Cambridge Greensand as Arca sulcata may be a 
dwarf race of this species. 
Perna lissa (Seeley). 
Fragmentary valves, indicating a very peculiar species about 
four inches long. Both valves are moderately convex, about as 
much so as in P. Crispi ; the right valve seemingly most inflated. 
The anterior side of the shell is truncated. Its axis is oblique, 
like that of an Avicula. It is gradually more compressed pos- 
teriorly, and quite smooth, or only marked with a few regular im- 
brications of growth like those in the Chalk shell Perna striata. 
Its affinities are with P. ¢enuwis on the one hand, and with P. 
transversa on the other. 
