64 THE NAUTILUS. 



MOLLUSKS COLLECTED BY R. C. MCGREGOR IN NORTHERN 



CALIFORNIA. 



BY HENRY A. PILSBRY. 



Mr. R. C. McGregor being engaged during the summer of 1898 

 in Fish Commission work which took him over a considerable area 

 in northern California, interested himself in the collection of inol- 

 lusks, which he sent me for study. 



The region is one which has been very superficially examined 

 hitherto, and it is not surprising that a number of very interesting 

 species were found. But few land shells were taken, among them 

 the extremely rare Polygyra roper i, and a peculiar Oircinaria. 

 Pyramidula striateUa occurred in many localities, the specimens be- 

 ing referable, probably, to the ill-defined variety cronkhitei. 



Among the fresh-water pulmonates, the re-discovery of Ancylus 

 patelloides Lea, a species falling into Clessin's genus Lanx, and A. 

 altus Tryon, also a Lanx, are the most important finds. These 

 species will be fully treated elsewhere, with illustrations of the 

 anatomy. 



The series of Gom'obases collected induced me to attempt a revision 

 of the West American species, the results of which are included below. 



The list of species is as follows : 



Epiphragmophora mormonum (Pfr.). Redding, Shasta Co. 



Polyyyra loricata (Gld.). Battle Creek, s. boundary Shasta Co. 



Polygyra ropen ,'(Pils.). Redding, Shasta Co. One adult specimen. 



Vallonia pukhella (Mull.). Redding, Shasta Co. 



Oircinaria sp. undet. Redding. I cannot refer the single fresh 

 adult shell collected to any of the described forms. 



Pyramidula striateUa (Anth.). Goose Lake, Modoc Co.; Duck 

 Lake, 20 miles west of Susanville, and Eagle Lake, Lassen Co.; 

 Bartle's, Siskiyou Co., on McCloud River. 



Vitrea hammonis (Strom). Bartle's and Duck Lake. 



Vitrina pfeijf'eri Newc. Bartle's and Duck Lake. 



Zonitoides arboreus (Say). Goose Lake, Modoc Co. 



Succinea nuttalliana (Lea). Goose Lake, Modoc Co. 



Succinea stretchiana (Bid.). Duck Lake and Bartle's. 



Limntea stagnalis (L.). Upper waters of "Willow Creek, trib. to 

 Susan R., Lassen Co. 



IJmncea proximo (Lea). South Fork Pitt R., Modoc Co. 



