5 2 . 0. lurida Carpenter
l 1 I n cross-section, the ribbon-like faeces of the oyster and mussel
showed marked longitudinal gro(o)ves and ridges ; . . . . ” (Edge, 1934,
p. 80, Fig. 2 . ) (Pellet-type 111-l0a).
53. Crassostrea gigas (Thunberg) (Pl. 4-41 ; Fig. 17, top, p. 400)
“At first sight, this species appears to void typical rod-shaped
pellets, but closer examination of cross-sections of pellets shows that
they are rather of a modified ribbon type. The ventral side of pellets
is smoothly surfaced and unsculptured, while the dorsal side is marked
by two deep longitudinal grooves embracing a low narrow longitudiiial
ridge in between them. This structure is, however, easily overlooked,
as it is wholly covered by well-developed lateral wings of the ribbon.
Both edges of the ribbon upcurled over the dorsal side may touch each
other and thus the real dorsal side of the pellet is entirely concealed.
The pellets are rather stiff in consistency, voided usually in short
pieces, and coloured orangy yellow. They are made of undetermined
well-digested materials mixed with numerous diatom frustules and
other skeletal matter. I n section, there is found a concentration of
coarser materials towards the centre. The average diameter of pellets
shed by an examined animal is 0.78 mm.
“ Remarks : anatomical examination of the alimentary canal of
this species demonstrates clearly that the shape of the faecal pellet is
determined by the internal structure of the canal. I n P1. VI. Fig. 1,
is shown a cross-section of the alimentary canal of a well-fed animal.
Here the canal is expanded and roughly rounded in outline, and two
prominent typhlosoles applying to two deep longitudinal grooves on
the dorsal side of the pellet are shown distinctly. Then, a cross-section
of the canal of a starved animal is shown in Fig. 2 ; now the canal is
much more flattened and shows the structure to yield thin ribbonshaped faeces. Finally in Fig. 3, a section of the canal of the animal
infected by some parasitic worms is given ; the ventral structure of t’he
canal is deformed and the lumen is narrowed tjo produce only flocculent
faeces of indefinite shape. Further, a cross-section of the gut of Ostren
denselamellosa is presented in Fig. 6 ; this structure is supposed to yield
flattened ribbon-shaped pellets with a bi-crescentic section.” (Arakawa,
1965, pp. 16-17, P1. V, Figs. 48-50, P1. VI, Figs. 1-5.) (Pellet-type
111-10a).
54. C . virginiea Gmel.
“ The feces of the oyster are voided from the rectum as a compact
and slightly flattened ribbon of sufficient consistency to withstand the
l 1 I n cross-section, the ribbon-like faeces of the oyster and mussel
showed marked longitudinal gro(o)ves and ridges ; . . . . ” (Edge, 1934,
p. 80, Fig. 2 . ) (Pellet-type 111-l0a).
53. Crassostrea gigas (Thunberg) (Pl. 4-41 ; Fig. 17, top, p. 400)
“At first sight, this species appears to void typical rod-shaped
pellets, but closer examination of cross-sections of pellets shows that
they are rather of a modified ribbon type. The ventral side of pellets
is smoothly surfaced and unsculptured, while the dorsal side is marked
by two deep longitudinal grooves embracing a low narrow longitudiiial
ridge in between them. This structure is, however, easily overlooked,
as it is wholly covered by well-developed lateral wings of the ribbon.
Both edges of the ribbon upcurled over the dorsal side may touch each
other and thus the real dorsal side of the pellet is entirely concealed.
The pellets are rather stiff in consistency, voided usually in short
pieces, and coloured orangy yellow. They are made of undetermined
well-digested materials mixed with numerous diatom frustules and
other skeletal matter. I n section, there is found a concentration of
coarser materials towards the centre. The average diameter of pellets
shed by an examined animal is 0.78 mm.
“ Remarks : anatomical examination of the alimentary canal of
this species demonstrates clearly that the shape of the faecal pellet is
determined by the internal structure of the canal. I n P1. VI. Fig. 1,
is shown a cross-section of the alimentary canal of a well-fed animal.
Here the canal is expanded and roughly rounded in outline, and two
prominent typhlosoles applying to two deep longitudinal grooves on
the dorsal side of the pellet are shown distinctly. Then, a cross-section
of the canal of a starved animal is shown in Fig. 2 ; now the canal is
much more flattened and shows the structure to yield thin ribbonshaped faeces. Finally in Fig. 3, a section of the canal of the animal
infected by some parasitic worms is given ; the ventral structure of t’he
canal is deformed and the lumen is narrowed tjo produce only flocculent
faeces of indefinite shape. Further, a cross-section of the gut of Ostren
denselamellosa is presented in Fig. 6 ; this structure is supposed to yield
flattened ribbon-shaped pellets with a bi-crescentic section.” (Arakawa,
1965, pp. 16-17, P1. V, Figs. 48-50, P1. VI, Figs. 1-5.) (Pellet-type
111-10a).
54. C . virginiea Gmel.
“ The feces of the oyster are voided from the rectum as a compact
and slightly flattened ribbon of sufficient consistency to withstand the