362
KOHMAN Y. ARAKAWA
in a short chain. They are rather coarse in texture and dark greenishbrown in colour, sometimes variegated by greyish patches. The
length/breadth ratio averages 1.49 (Pellet-type 1-1).
Locality : Chijiwa Bay (20 m deep), Kumamoto, Japan.
Measurements when size of producer is 21.2 mm in shell length :
Length of pellet (mm)
0.52 0.56 0.47 0.53 0.48 0.54
Breadth of pellet (mm)
0.35 0.35 0.35 0.35 0.35 0.35
Ratio length/breadth
1.49 1.60 1.42 1.52 1-37 1.54
Mesodesmatidae
144. Caecella chinensis Deshayes (Pl. 4-51)
“ The pellets are dark brown in colour, fine in texture and greatly
variable in shape. Most frequently faeces are voided in a form of rod,
but occasionally in roundish pellets with blunt ends or sometimes with
one end blunt and the other sharply pointed. They are composed entirely of fine detritus.” (Arakawa, 1963, p. 207, Text-fig. 6, H-K)
(Pellet-type 11-4).
Mactridae
In this family there are two distinct types of faecal pellet. According
to Edge (1934), the pellets of Schizothaerus are rod-like with a linear
segmentation (Type IA-3), unlike those described here for other representatives of this family. In Muctra, the faeces are ellipsoid or ovoid
and belong to Type 1-2. The major difference between species lies in
the length/breadth ratio of the pellets.
145. Mactra sulcatariu Rve (PI. 3-33 ; Fig. 15, p. 398)
The pellets are elongate ellipsoid, parallel-sided and truncated at
both ends. Occasionally they are impressed indistinctly on the surface
by a single right-hand spiral stria. They are made up almost entirely
of fine grade detritus. Average length/breadth ratio is 2.09 (Pellettype 1-2).
Locality : Tomioka, Kumamoto, Japan.
Measurements when size of producer is 23.0 mm in shell length :
Length of pellet (mm)
Breadth of pellet (mm)
0.46 0.46 0.46 0.46 0.49 0.46 0.46 0.46
Ratio length/breadth 2.57 2.13 1.98 2.37 2.39 1.59 1-98 1.74
1.18 1.00 0.91 1.09 1.17 0.73 0.91 0.80
KOHMAN Y. ARAKAWA
in a short chain. They are rather coarse in texture and dark greenishbrown in colour, sometimes variegated by greyish patches. The
length/breadth ratio averages 1.49 (Pellet-type 1-1).
Locality : Chijiwa Bay (20 m deep), Kumamoto, Japan.
Measurements when size of producer is 21.2 mm in shell length :
Length of pellet (mm)
0.52 0.56 0.47 0.53 0.48 0.54
Breadth of pellet (mm)
0.35 0.35 0.35 0.35 0.35 0.35
Ratio length/breadth
1.49 1.60 1.42 1.52 1-37 1.54
Mesodesmatidae
144. Caecella chinensis Deshayes (Pl. 4-51)
“ The pellets are dark brown in colour, fine in texture and greatly
variable in shape. Most frequently faeces are voided in a form of rod,
but occasionally in roundish pellets with blunt ends or sometimes with
one end blunt and the other sharply pointed. They are composed entirely of fine detritus.” (Arakawa, 1963, p. 207, Text-fig. 6, H-K)
(Pellet-type 11-4).
Mactridae
In this family there are two distinct types of faecal pellet. According
to Edge (1934), the pellets of Schizothaerus are rod-like with a linear
segmentation (Type IA-3), unlike those described here for other representatives of this family. In Muctra, the faeces are ellipsoid or ovoid
and belong to Type 1-2. The major difference between species lies in
the length/breadth ratio of the pellets.
145. Mactra sulcatariu Rve (PI. 3-33 ; Fig. 15, p. 398)
The pellets are elongate ellipsoid, parallel-sided and truncated at
both ends. Occasionally they are impressed indistinctly on the surface
by a single right-hand spiral stria. They are made up almost entirely
of fine grade detritus. Average length/breadth ratio is 2.09 (Pellettype 1-2).
Locality : Tomioka, Kumamoto, Japan.
Measurements when size of producer is 23.0 mm in shell length :
Length of pellet (mm)
Breadth of pellet (mm)
0.46 0.46 0.46 0.46 0.49 0.46 0.46 0.46
Ratio length/breadth 2.57 2.13 1.98 2.37 2.39 1.59 1-98 1.74
1.18 1.00 0.91 1.09 1.17 0.73 0.91 0.80