Pvn H,i I'UitlS

DONAX. 401
" Marginales utrinque solitarii, remoti a Cardinalibus,
distincti fossula in ipso margine." It is the T. varu
abilis of Pulteney, T.depressa of Pennant, Solen pictus
of Spengler, T. gari of Poli (but not of Linne), Psam-
mobia florida of Lamarck, and T. albida of Dilhvyn (but
not of Linne). Leach proposed the generic name of
Gobrceus for the present species.
Sanguinolaria deflorata is a tropical shell, and was
wrongly
introduced into the British fauna.
Genus IV. DO'NAX*, Linne. PI. VII. f. 5.
Body oblong, compressed, rather thick : mantle having a
double margin, the outer one of which is clothed with three
rows of fringe : tubes not so long as in the other genera, lon-
gitudinally lineated ;
orifices cirrous.
Shell wedge-shaped, equivalve, inequilateral, rather solid,
mostly smooth and covered with a glossy epidermis, but some-
times and partially sculptured by longitudinal striae, some of
which are decussated by concentric strire : posterior side ob-
liquely truncate : teeth consisting
of a double and central car-
dinal, with a slight diverging laminar one on either side in the
right valve, and two diverging cardinals (representing a reversed
V) with a minute tooth between them at their junction
in the left valve, besides laterals on each side of both valves
near the beaks : inside having the margin usually more or less
notched or crenulated.
Systematists are not agreed as to whether this genus
should constitute the type of a family apart from the
TeUinidce. It is bv no means easv to say how many
and what kind of characters are essential for the formation
of such a group. The animal of Donax resembles
that of Psammobia, especially in the ciliated lines of
the tubes or siphons ; but the mantle has an outer and
inner margin, the former being ornamented with three
rows of cirri : the shell is not unlike that of some species
* A kind of fish mentioned bv Athena'us.