| 1a |
Rasping anterior
portion of valves
abruptly separated by a groove from the non-rasping portion (photo) |
2 |
| 1b |
Rasping anterior
portion of valves
not abruptly separated from the non-rasping portion (burrowing in firm
mud or clay; length to about 5 cm; not likely to be found north of
southern
Washington) |
Barnea (Anchomasa) subtruncata |
| 2a |
Without a myophore
(apophysis)
in either valve;
posterior portion of shell, in mature specimens, tapering to a point,
thus
resembling a bird's beak; anterior
portion of shell gaping as if abruptly cut off; siphonoplax
(consisting of a pair of flaps that enclose the siphons)
calcified |
Netastoma rostrata |
| 2b |
With a myophore
(photo)
in both valves;
posterior portion of shell not tapering sufficiently to resemble a
bird's
beak (it may taper, however, especially in Pholadidea conradi);
anterior
portion of shell gaping (photo)
(except in full-grown specimens, in which the gape is closed by a callum),
but not appearing to have been abruptly cut off; siphonoplax
not calcified |
3 |
| 3a |
Rasping anterior
portion of each valve
occupying about half the area of the valve;
valves without a shieldlike plate (protoplax)
dorsal
to the rasping portion; anteroventral
gape not becoming closed, when the animal is full grown, by a callum;
length up to 15 cm; burrowing in firm mud or clay |
Zirfaea
pilsbryi |
| 3b |
Rasping portion of each valve
occupying less than half the area of the valve
(photo);
valves
with a thick, shieldlike plate (protoplax)
dorsal
to the rasping portion (photo);
anteroventral
gape (photo)
becoming
closed, in full-grown specimens, by a callum;
length not exceeding 8 cm; generally boring in shale, sometimes in hard
clay |
4 |
| 4a |
Posterior
(siphonal)
ends
of valves
of mature
specimens with a siphonoplax
(this consists of a pair of flaps that enclose the siphons);
siphons
smooth |
5 |
| 4b |
Posterior
ends of valves
of
mature specimens without a siphonoplax;
siphons
smooth or slightly warty |
6 |
| 5a |
Siphonoplax
consisting of flexible flaps, not lined by calcareous granules; length
to about 8 cm; generally boring in shale |
Penitella
penita |
| 5b |
Siphonoplax
not flexible, lined with calcareous granules; length to about 2.5 cm;
generally
boring in shells of abalones (Haliotis), Mytilus
californianus, and other molluscs. |
Penitella conradi |
| 6a |
Siphons
smooth;
umbonal
reflections (calcified plates between the protoplax
and the rasping portion of each valve)
tightly applied to the shell (Note: What was formerly called
a protoplax
on this species is now recognized as a dorsal
extension of the callum--this
species does not actually have a protoplax) |
Penitella
turnerae |
| 6b |
Siphons
warty;
umbonal
reflections free of the shell for about half their length (P.
gabbi
in original key) |
Penitella richardsoni |
