9. THE CLASS CRUSTACEA
201
Wilson (1938), unaware of Mori’s M . orientalis, described M . ostreae
from the intestine of Crassostrea gigas which had been imported to
Puget Sound, Washington, from Japan. Wilson’s description is sufficiently similar to that of M . orientalis so that Odlaug (1946) has suggested that the two species are identical. After having analyzed both
descriptions and compared the original illustrations, I am in agreement
with Odlaug that M . ostreae is a synonym of M . orientalis. This
parasite is widely spread in Puget Sound where it occurs in Mytilus
edulis, Crassostrea gigas, Ostrea lurida, Venerupis ( = Paphia) staminea
FIG. 189. Cross-section of Mytilicola intestinalis in stomach o f Crassostrea giga.8 f r o m
Washington. (Slide courtesy of Dr. Kenneth K . Chew, University of Washington.)
and Crepidula fornicnta. It has also been reported in Mytilus californianus collected in Humboldt Bay, California (Chew et al., 1963).
Description. Adult female (Fig. 190), 10-12 mm in total length,
1-33 in greatest width (fourth segment), with elongate narrow body,
tapering posteriorly ; head separated from thorax, wider than long,
with small dorsal carapace divided longitudinally through its center ;
five thoracic segments and genital segment completely fused, with a pair
of posterolateral protuberances (processes) on each of the five thoracic
segments, these being more prominent than those of M . intestinalis,
201
Wilson (1938), unaware of Mori’s M . orientalis, described M . ostreae
from the intestine of Crassostrea gigas which had been imported to
Puget Sound, Washington, from Japan. Wilson’s description is sufficiently similar to that of M . orientalis so that Odlaug (1946) has suggested that the two species are identical. After having analyzed both
descriptions and compared the original illustrations, I am in agreement
with Odlaug that M . ostreae is a synonym of M . orientalis. This
parasite is widely spread in Puget Sound where it occurs in Mytilus
edulis, Crassostrea gigas, Ostrea lurida, Venerupis ( = Paphia) staminea
FIG. 189. Cross-section of Mytilicola intestinalis in stomach o f Crassostrea giga.8 f r o m
Washington. (Slide courtesy of Dr. Kenneth K . Chew, University of Washington.)
and Crepidula fornicnta. It has also been reported in Mytilus californianus collected in Humboldt Bay, California (Chew et al., 1963).
Description. Adult female (Fig. 190), 10-12 mm in total length,
1-33 in greatest width (fourth segment), with elongate narrow body,
tapering posteriorly ; head separated from thorax, wider than long,
with small dorsal carapace divided longitudinally through its center ;
five thoracic segments and genital segment completely fused, with a pair
of posterolateral protuberances (processes) on each of the five thoracic
segments, these being more prominent than those of M . intestinalis,