30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 95 



mollusks in question, nevertheless, are as different from each of these 

 as these differ among themselves. It is for this reason that I propose 

 the generic name Schistosomophora for them. 



In 1895 von Mollendorff (lo) described, among other minute 

 operculates, Prososthenia quadrasi from near the tovi^n of Surigao, 

 northeastern Mindanao, Philippine Islands. Little did he suspect the 

 important role that this insignificant-looking snail v^ould be found 

 to play in the health of this region. We, therefore, find little beyond 

 a mere listing of the species in catalogs of mollusks until Tubangui 

 (40) established its intermediate host status in his paper on " The 

 Molluscan Intermediate Host in the Philippines of the Oriental Blood 

 Fluke Schistosoiiia japonicum Katsurada." 



Following Tubangui, Rensch (41), to whom some of these mol- 

 lusks were sent for determination, christened them Oncomelania 

 hydrohiopsis in 1932. 



In 1934 Bequaert (44) published " The Molluscan Intermediate 

 Host of the Blood Fluke, Schistosoma japonicum Katsurada ", 

 where he calls it Blanfordia quadrasi, and makes Oncomelania hydro- 

 hiopsis Rensch synonymous with it. 



GENERIC DEFINITION 



Shell. — Shell small, elongate-ovate, thin, horn-colored or darker, 

 with a slender dark line bordering the peristome. Nuclear whorls 

 2.0, inflated, strongly rounded, glassy, appearing finely granulated 

 under very high magnification. Postnuclear whorls inflated, well 

 rounded, marked by retractively slanting lines of growth, which in 

 hydrohiopsis assume almost the strength of threads. In this they are 

 rather coarse and closely approximated. In the other two species the 

 indication of axial sculpture, although similar, is very much reduced, 

 that is, merely indicated. Suture strongly constricted; periphery in- 

 flated, well rounded. Base short, inflated, strongly rounded, narrowly 

 umbilicated. There is a thickening of the outer lip behind the aperture 

 into a callus, which is scarcely indicated in minima. 



Operculum. — Operculum thin, horny, paucispiral, consisting of 

 only 1.5 whorls, which have the nucleus excentric. 



Radida. — The radula is small and has a rachidian tooth with 5 

 denticles, of which the middle one is the largest and the other two 

 decrease in size. There are only 2 basals on each side present in this 



