| 1a |
With distinct radial
ribs (these may, however, be delicate or faint) |
2 |
| 1b |
Without radial
ribs |
4 |
| 2a |
Radial ribs typically more prominent than the concentric ridges (but
this is not always the case); hinge ligament about 1/3 the length of the
shell; length not more than 6 cm |
3 |
| 2b |
Radial ribs less prominent than the concentric ridges; hinge ligament
nearly half the length of the shell; length sometimes attaining 8 cm |
Protothaca (Callithaca)
tenerrima |
| 3a |
With a row of small teeth on the inside of the valves close to their
ventral margins; interior of valves whitish, without a purple stain near
the posterior end |
Leukoma staminea |
| 3b |
Without a row of teeth on the inside of the valves close to their ventral
margins; interior of valves (often) yellowish, with a purple stain near
the posterior end. [In key as Tapes (Ruditapes)
philippinarum] |
Venerupis philippinarum |
| 4a |
Length
less than 8 mm; height
usually more than 3/4 the length;
angle formed by the dorsal
margin at the umbones
not more than 110 degrees; 3 cardinal
teeth on the hinge
plate of both valves; embryos brooded internally |
5 |
| 4b |
Length
generally greater than 2 cm; height
not often more than 3/4 the length;
angle formed by the dorsal
margin at the umbones
more than 110 degrees |
8 |
| 5a |
|
|
| 5b |
|
|
| 6a |
|
|
| 6b |
|
|
| 7a |
|
|
| 7b |
|
|
| 8a |
Concentric ridges conspicuously raised; posteriormostcardinal
tooth on right valve
not
bifid |
9 |
| 8b |
Concentric lines of growth not conspicuously raised, the exterior of
the shell thus nearly smooth; posteriormostcardinal
tooth on right valvebifid
(length
up to about 6 cm) |
Compsomyax subdiaphana |
| 9a |
Umbones at the
end of the second 1/5 of the shell from the anterior
end; periostracum
yellowish, polished; length
up to 2.5 cm; subtidal |
Liocyma fluctuosa |
| 9b |
Umbones at the
end of the first 1/5 of the shell from the anterior
end; periostracum
not yellowish and not polished; length
generally exceeding 3 cm |
10 |
| 10a |
Shell closing tightly at the posterior
end; concentric ridges bent in the direction of the umbones;
length
up to 10 cm; subtidal |
Humilaria kennerlyi |
| 10b |
Shell gaping slightly at the posterior
end; concentric ridges, even if sharp, not bent in the direction of the
umbones;
length
often exceeding 10 cm; common intertidally |
Saxidomus gigantea
(S. giganteus in key) |