SCATOLOGICAL STUDIES OF THE BIVALVIA (MOLLUSCA)
326
41. 8. (Mytilisepta) keenae (Nomura) (PI. I-!))
Pellets of this species are very similar in type to those of the preceding and the following ones. The external sculpture is prominent
and the section is bi-crescentic (Pellet-type III-1Oa).
Locality : Tomioka, Kumamoto, Japan.
Measurements: For animals with 41.0 mm long shells, width of the
ribbons fluctuates between 0.71 and 0.75 mm.
42. 8. ( M . ) virgatus (Wiegmann) (Pl. 4-39)
" The faeces are ribbon-shaped, and very friable in consistency ;
the central portion is thicker than other parts and folded on the side
corresponding to the dorsal side of the alimentary tract to form a middorsal ridge, and a shallow but wide mid-ventral groove on the opposite
side. The free edges slightly turn up dorsalwards so that the ribbon
assumes a bi-crescent-shape in cross-section. For an animal 16.5 mm
long, the pellets average 0.64 mm in width.'' (Arakawa, 1963, p. 205,
Text-Fig. 6, A-B.) (Pellet-type III-loa).
43. Volsella americana Leach
" 1 animal. This animal shed pellets which resemble more closely
those described by Moore (1931) for M . phaseolinus. The ribbon is
thickened laterally and possesses the median longitudinal thickening on
one surface and the slight groove opposing it on the other surface. The
ribbon was broken into pieces 0-32 to 0.43 mm." (Manning and Kumpf,
1959, p. 301, Fig. 4g.) (Pellet-type I I I - 1 0 ~ ) .
Isognomonidae (Vulsellidae)
Three representatives of this group produce ribbon-like pellets with
a median longitudinal groove and with slightly upcurled edges (Pellettype III-1Oa).
44. Isognomon data Gmelin
" 1 animal. The faecal matter of this specimen was too flocculent
to allow drawings to be made. However, some small portions of a ribbon were observed. Those of the closely related Isognomon radiata are
described below." (Manning and Kumpf, 1959, p. 301 .) (Pellet-type
III-lOa.)
45. I . radiata Anton
" 3 animals. Because of the shape of the animals, only the largest
measurement was taken. An animal with a maximum measurement of
326
41. 8. (Mytilisepta) keenae (Nomura) (PI. I-!))
Pellets of this species are very similar in type to those of the preceding and the following ones. The external sculpture is prominent
and the section is bi-crescentic (Pellet-type III-1Oa).
Locality : Tomioka, Kumamoto, Japan.
Measurements: For animals with 41.0 mm long shells, width of the
ribbons fluctuates between 0.71 and 0.75 mm.
42. 8. ( M . ) virgatus (Wiegmann) (Pl. 4-39)
" The faeces are ribbon-shaped, and very friable in consistency ;
the central portion is thicker than other parts and folded on the side
corresponding to the dorsal side of the alimentary tract to form a middorsal ridge, and a shallow but wide mid-ventral groove on the opposite
side. The free edges slightly turn up dorsalwards so that the ribbon
assumes a bi-crescent-shape in cross-section. For an animal 16.5 mm
long, the pellets average 0.64 mm in width.'' (Arakawa, 1963, p. 205,
Text-Fig. 6, A-B.) (Pellet-type III-loa).
43. Volsella americana Leach
" 1 animal. This animal shed pellets which resemble more closely
those described by Moore (1931) for M . phaseolinus. The ribbon is
thickened laterally and possesses the median longitudinal thickening on
one surface and the slight groove opposing it on the other surface. The
ribbon was broken into pieces 0-32 to 0.43 mm." (Manning and Kumpf,
1959, p. 301, Fig. 4g.) (Pellet-type I I I - 1 0 ~ ) .
Isognomonidae (Vulsellidae)
Three representatives of this group produce ribbon-like pellets with
a median longitudinal groove and with slightly upcurled edges (Pellettype III-1Oa).
44. Isognomon data Gmelin
" 1 animal. The faecal matter of this specimen was too flocculent
to allow drawings to be made. However, some small portions of a ribbon were observed. Those of the closely related Isognomon radiata are
described below." (Manning and Kumpf, 1959, p. 301 .) (Pellet-type
III-lOa.)
45. I . radiata Anton
" 3 animals. Because of the shape of the animals, only the largest
measurement was taken. An animal with a maximum measurement of