Occasional Papers of the Mtisciiiii of Zoology 7 



This p}"gmy species is an interestiui;' addition to the num- 

 ber of dwarf forms cliaracteristic of the arid region of the 

 western states. In size it may be compared with F. miiiii- 

 tissiina Pils., but differs entirely in shape and proi)ortions. It 

 was quite alnmdant in the one locahty where it was found. 



14. Margaritaiia maraarififcra (L.) — Humboldt River. 

 Only a few collected. 



15. Anodo)ita orcgoiiciisis Lea. — Humlioldt River. 

 Abundant. 



16. Splicvriuiit striatiiiiiiit- (Lam.) — ^larsh pond near the 

 Humboldt River: drift in river dam and mud flat along' the 

 river. 



"It appears that all of the shells are of the same species, 

 although of markedly different forms. I see no way of sep-. 

 arating them cleanly and so it is better not done. ^Nlost of the 

 specimens are much like 5'. striatiniun (Lam.), and if they 

 were from somewhere east, there would be barely a doubt 

 about it : that is, the more elongate and subequipartitc ones. As 

 stated, some are markcdl\" diftercnt. oblique, with the posterior 

 part nuich larger, higher and grown downward, much like S. 

 aciimiitatuiii ( Pnic. ) ; but there appear to l)e intermediate forms 

 and some eastern {Mississippi \'alley and eastward) forms. 

 ai)parentl_\- also of shiatiniim, arc much like those. Of course, 

 it sounds strange to take specimens from that region for 

 striatimiiii, but I have seen specimens occasionally from far 

 west, which appeared not separable from that species. Un- 

 fortunatel} , very little material is at baud from the intermediate 

 country and the Central and Pacific regions are insufficiently 

 known. So, for the present, it ai)])ears preferable to take 

 them for the species, which they resemble most, at least tenta- 

 tivelv. 



