108 THE NAUTILUS. 



species will be known as P. say ana Pils., hereafter, and that Pyra- 

 midvla striatella Anthony for like reason must give way to P. cronk- 

 hitei anthonyi Pils. 



Among the large number of new forms of land species described 

 the most remarkable is Bifidaria tuba, the type of a new subgenus 

 Chaenaxis, characterized by its "large hollow axis, open below and 

 about one-third the total diameter of the shell," found in the drift of 

 the San Pedro river, Cochise county, Arizona. 



Radiodiscus millecostatus from the Huachuca Mountains, Arizona 

 and Mexico, a minute Endodontid, is likewise both a new species 

 and the type of a new genus. 



The fresh-water forms of the region are also fully discussed, and 

 afford several novelties in Planorbis, Valvata, Amnicola and Palude- 

 strina, all minute, and some of them the smallest species yet dis- 

 covered. The several varieties of Lymncea bulimoides, — sonomaensis 

 Hemp., techella Hald., and cockerelli (new) — are fully differentiated 

 and figured, but unfortunately the typical form is neither figured nor 

 discussed comparatively. 



In Segmentina, attention is called to the difference in the character 

 of the apertural lamellae in the North American forms included in 

 s. g. Planorbula Hald., and in the Antillian and Mexican group rep- 

 resented in our fauna by S. obstructa (Morel.). In S. armigera and 

 wheatleyi the lamellae, though differing in development, are " funda- 

 mentally identical." The Section Haldemanina recently established 

 by Dali (Alaska, xiii, 97, 1905) for the latter species would therefore 

 seem to be a synonym of Planorbula Hald. 



The most important item in this portion of the paper is the dis- 

 covery of a species of Cochliopa (C. riograndensis) in the drift of the 

 Rio San Felipe, Val Verde County, Texas. The occurrence of C. 

 rowelli Tryon, a Central American species, in California lias always 

 been doubted. The present discovery confirms the genus as a mem- 

 ber of our fauna. 



The authors intimate that their discussion of the southwestern 

 mollusks will be concluded by a third paper. Its appearance will be 

 eagerly looked for by all students of our North American fauna. 

 But, unle-s their well-known skill in the field has deserted them, it 

 is confidently expected that the expedition of 1906 to the Grand 

 Canyon will yield results quite as important as did their former ones, 

 and that the fauna of the southwest will in the near future be still 

 further illuminated by their labors. Bryant "Walker. 



