Seen vertically from above, each shows a deep fold, which receives the lower part of the tergal margin of the scutum.
The claspers seem to be the tergal portions of the ninth segment.
This latter margin is slightly sinuous, and a little hollowed out towards the tergal corner of the valve.
Two pectoral feet somewhat smaller than the two tergal feet, about as long as the shell, slightly divergent, cylindrical.
tergal suture: the Y shaped dorsal suture on the head of many insect larvae.
Two frontal horns and two tergal feet about as long as the shell; odd horn shorter; odd foot longer.
Two tergal feet half as long and thick, simple (in the figure hidden behind the large pectoral feet).
In the basi-carinal corner of the valve there are often crests for the attachment of the tergal depressor muscle.
Internally, the articular ridge is prominent; the crests for the tergal depressores are feebly developed.
The crests for the tergal depressor muscles are either absent or very feebly developed.