_Cirrus Sac_--is the most characteristic feature of this species. It is a powerfully built, convoluted sac standing out clearly on the body. It is not a uniform, straight cylinder 0·25 to 0·33 mm. in diameter, as in _Fasciolopsis buski_, but even in fully extended flukes is typically convoluted. It is 1 mm. thick in the middle, but in other parts varies much from this. The posterior end of the cirrus sac is at two-thirds or more of the distance from ventral sucker to shell gland. In the case of _Fasciolopsis buski_ the posterior end of the sac only extends half-way. _Seminal Vesicle_--has a peculiar convoluted, saccular and angular course, but the cæcal appendage characteristic of the genus appears to be absent! _Excretory System._--The main stem gives off very regular transverse branches which are well seen posteriorly. _Eggs._--100 µ by 73 µ. Thin shelled. _Habitat._--Intestine. Mahommedan from Calcutta. [It is evident that a re-examination of fresh material is required before the validity of all these species can be accepted.--J. W. W. S.] Family. *Troglotremidæ*, Odhner, 1914. Genus. *Paragonimus*, Braun, 1899. Body egg-shaped or somewhat elongated, generally more broadly rounded in front than behind. Covered all over with spear-shaped spines _arranged in groups_. Gut cæca winding with dilatations or constrictions in parts. Ventral sucker in or in front of the middle of the body. Excretory bladder cylindrical, very long and broad, reaching in front to the bifurcation of the gut. The lateral excretory canals join the bladder only a little in front of the excretory pore. Genital pore median just behind the ventral sucker. Genital sinus duct-like. Cirrus sac absent. Male terminal organs very small. Ejaculatory duct present. Testes and ovary deeply lobed, the testes in or just behind the middle, the ovary somewhat laterally placed just _behind_ the ventral sucker. Uterus forms a coil behind the ventral sucker. Eggs rather large, thin shelled, the ovarian cell still unsegmented on deposition. Receptaculum seminis, small. Parasitic in the lungs of mammals, enclosed in cyst-like cavities, generally in pairs. _Type Species._--_P. westermanii_ in the tiger. *Paragonimus ringeri*, Cobb., 1880. Syn.: _Distoma ringeri_, Cobb., 1880; _Distoma pulmonale_, Baelz, 1883; _Distoma pulmonis_, Suga, 1883.