a ae 
Armigerus obstructus (Morelet) 
Plate IV, J 
Shell relatively small and disk-shaped, rather glossy, whitish to light 
brown or olive horn, sculptured with fine spiral striae and growth lines. 
The spire is depressed below the body whorl, the sutures impressed. 
Aperture rather deeply lunate, usually with lamellae or teeth. Adults 
(with 5-6 whorls) are 5-8 mm. wide. 
Distribution: Louisiana, Texas, Mexico, Guatemala, 
This species is closely related to snails of the genus Biomphalaria and 
Planorbina and may be cogeneric with these groups. 
Biomphalaria boissyi Potiez and Michaud 
(Afroplanorbis, B, alexandrina) 
Plate IV, K 
The shell is similar to Armigerus obstructus but is larger and its aper- 
ture lacks teeth. Adults (with 5-6 whorls) are 18-22 mm. in diameter. 
Distribution: Egypt, the Sudan. 
This species and Physopsis africana and Bulinus truncatus are the main 
carriers of the human blood fluke in Africa. 
Planorbina (Australorbis, Taphius) glabrata (Say) 
(= Biomphalaria boissyi) 
Plate IV, I 
The shell of this species is identical to that of Biomphalaria boissyi, but 
often becomes much larger, adults measuring up to 35 mm, in diameter. 
Distribution: West Indies, northern South America. 
This species is the carrier of the human blood fluke in the tropics of this 
hemisphere, 
