240
MARINE MOLLUSCS AS HOSTS BOR SYMBIOSES
pharynx, pharynx, and long esophagus present ; pharynx 0.025 mm
long x 0-016 mm wide ; intestinal caeca long, reaching to near posterior
end of body ; excretory vesicle Y-shaped, with arms reaching anteriorly
FIas. 143-150. Fellodistomatid and echinostomatid trematode larvae. (143) Cercaria
brwhidontis (redrawn after Hopkins, 1954b) ; (144) Himasthla leptosoma metacercaria
within cyst (redrawn after Lebour, 1911) ; (145) H . quissetensis metacercaria within
cyst; (146) H . ambigua metacercaria within cyst ; (147) H . ambigua metacercaria
removed from cyst (redrawn after Palombi, 1934s) ; (148) unidentified echinostome
metacercaria of Nicoll (redrawn after Nicoll, 1906a) ; (149) encysted Parorchis
acanthus metacercaria, frontal view ; (150) encysted P. ancanthus metacercaria,
lateral view showing characteristic flat surface (redrawn after Stunkard awd Cable,
1932).