86 PROCEEDINGS OF THE ACADEMY OT [VOL. LXXIV 



grounds to full generic rank by Pilsbry and Ferriss (:08, p. 135-136), 

 who refer to it not only the typical species found on the southern 

 California coast and islands, but also the desert forms of the 

 Colorado basin. Tentatively admitting the propriety of this 

 arrangement, at least until the proper relationship of all the 

 western dart-bearing Helices to the more austral true Epiphragmo- 

 phoras becomes more clear than I believe it to be at present, 

 there still seem to exist abundant reasons for a further separation 

 of the two very distinct Californian groups of Micrarionta into 

 subgenera. All the species known fall easily into one or the other 

 of these, the maritime species into Micrarionta s. s., the desert 

 ones into Pilsbry 's group Eremarionia. 



Subgenus EREMARIONTA Pilsbry 1913 



Shell almost always whitish or pale fawn colored or light brown, 

 with a darker band above the periphery. Spiral sculpture wanting. 

 Nuclear whorls sculptured with curiously formed, elongate papillae, 

 sometimes bearing hair-like periostracal projections, and arranged 

 in oblique, forward slanting lines, the radial sculpture being 

 generally relatively inconspicuous. 



Type: Micrarionta desertorum Pilsbry and Ferriss. 



To judge from the nature of the shell characters, and especially 

 the details of the embryonic sculpture, all the following previously 

 described species seem referable to Eremarionta. The anatomy, 

 however, has been investigated (by Pilsbry) only in the case of 

 the first three: Micrarionta desertorum Pilsbry and Ferriss, Sono- 

 rella wolcottiand Bartsch, Micrarionta hutsoni Clapp, Epiphragmo- 

 phora harperi Bryant, Sonorella (baileyi) orcutti Bartsch, Helix 

 (( 'arpenteri, var.) Indiocnsis Yates, Sonorella argus Edson, Mic- 

 rarionta rixfordi Pilsbry. 



To these should logically be added Sonorella baileyi Bartsch and 

 Sonorella fisheri Bartsch, which I have not seen, and the two new 

 species to be described, with perhaps also the Epiphragmophora 

 bmversi Bryant, the whole forming a rather weakly differentiated 

 concourse of species entirely confined to the desert regions border- 

 ing the Colorado River and its basin, in southeastern California 

 and western Arizona. 



On the other hand the species of typical Micrarionta are all 

 maritime and in their distribution well separated from the Eremar- 

 ionta group, unless, as there are reasons for suspecting, the numerous 

 Lower California Helices now generally referred to Sonorella 



