s Ap # 
Family PLEUROCERIDAE 
This family contains medium to large aquatic snails with rather solid, 
thick, conical to globose shells with corneous opercula, It is widely dis- 
tributed with species in North, Central, and South America, Africa, and 
Asia. The genus of prime medical importance is Semisulcospira, which, 
along with Melanoides and Tarebiaof the family Thiaridae, is often called 
Melania in the older literature. One species, Semisulcospira libertina, 
is the main vector of paragonimiasis, the human lung fluke disease in the 
Orient. 
Semisulcospira libertina (Gould) 
Figure, 15 
Shell large, imperforate, with rather flattened whorls and unimpressed 
sutures, sculptured with many small, raised, spiral lines (lirae) and often 
with low transverse wrinkles. The tip of the spire is often eroded away. 
Color light yellowish-brown to almost black. Operculum paucispiral, thin, 
dark brown, the nucleus near the base. Uneroded adults (with 9-12 whorls) 
measure 30-50 mm. in height. 
Distribution: Japan, Korea, Okinawa, Formosa. 

Figure 15, - Shell of Semisulcospira libertina (Gould) 
