26
PANDORID^.
ser. Zool. ii.)^ remarks with respect to this species, that
the outer gill, which resembles a hood, might at first
sight be taken for a single leaf, so disproportionately
small is its size.
He considers it a case of arrested
development.
Mr. Jordan says, "Whilst collecting
specimens at Jersey, I noticed that they have a habit of
squirting, like Saxicava rugosa and the Pholades when
first touched ; one individual ejected a fine stream, fully
sixteen inches high."
In Mr. Clark^s description of the
animal of var. obtusa the tubes are stated to be fringed
at their orifices with fine white short cirri ; the margin
of the sheath, in some specimens, is marked by a fine
orange line; and the base of the cirri and margins of
the orifices are usually encircled by a dead-white narrow
thread.
The ovary is of a reddish-brown colour. I
found it to contain in July an immense mass of vesicular
ova in difi'erent states of growth ; the more forward of
them resembled in shape some species of Cythere. Adult
specimens vary in their comparative length and proportions, as well as in the prominence of the ridges on the
dorsal side.
The diff'erence between the typical shell
and the variety obtusa apparently arises fi'om the nature
of their respective habitats—the one being sublittoral,
and the other belonging to deeper water. An intermediate form has been taken by Cailliaud on the coast
of Brittany, and by M^Andrew at Corunna. On a
superficial view, indeed, it would seem as if a valid
distinction existed in the length from the beak to the
front margin being always greater in P. incequivalvis (or
rostrata), and on the posterior side in P. obtusa ; but
this only shows that varieties, as well as species, have
some one character of their own. Such may be expected
when the conditions of life vary. The extension of the
posterior side in the typical form may be caused by the
PANDORID^.
ser. Zool. ii.)^ remarks with respect to this species, that
the outer gill, which resembles a hood, might at first
sight be taken for a single leaf, so disproportionately
small is its size.
He considers it a case of arrested
development.
Mr. Jordan says, "Whilst collecting
specimens at Jersey, I noticed that they have a habit of
squirting, like Saxicava rugosa and the Pholades when
first touched ; one individual ejected a fine stream, fully
sixteen inches high."
In Mr. Clark^s description of the
animal of var. obtusa the tubes are stated to be fringed
at their orifices with fine white short cirri ; the margin
of the sheath, in some specimens, is marked by a fine
orange line; and the base of the cirri and margins of
the orifices are usually encircled by a dead-white narrow
thread.
The ovary is of a reddish-brown colour. I
found it to contain in July an immense mass of vesicular
ova in difi'erent states of growth ; the more forward of
them resembled in shape some species of Cythere. Adult
specimens vary in their comparative length and proportions, as well as in the prominence of the ridges on the
dorsal side.
The diff'erence between the typical shell
and the variety obtusa apparently arises fi'om the nature
of their respective habitats—the one being sublittoral,
and the other belonging to deeper water. An intermediate form has been taken by Cailliaud on the coast
of Brittany, and by M^Andrew at Corunna. On a
superficial view, indeed, it would seem as if a valid
distinction existed in the length from the beak to the
front margin being always greater in P. incequivalvis (or
rostrata), and on the posterior side in P. obtusa ; but
this only shows that varieties, as well as species, have
some one character of their own. Such may be expected
when the conditions of life vary. The extension of the
posterior side in the typical form may be caused by the