IIIK NAUTILUS. 125 



extends about oiie-fiftli of the circumference of tlie last wliorl. Tl.e 

 aperture is nearly circular, interrupted for a short distance by the 

 body, the inner lip slightly reflected over a small umbilicus ; tbe 

 operculum is multispiral and pale yellow. Alt. of shell 6.0 ; of 

 aperture, 3.0 ; max. diam., 5,5 mm. 



This species is somewhat like S. umbilicata JefTreys from the 

 North Atlantic, but is larger, more strongly sculptured and more 

 elevated proportionately. It is the second species of the family to 

 be described from the Pacific Coast ; the other Schismope rtmuloides 

 Carpenter having been reported from .San Diego and Mazatlan. It 

 is named in honor of Prof. F. W. Kelsey, of San Diego, to whose 

 interest in the local mollusks we owe several additions to that fauna. 



CRITICAL NOTES ON THE SMALLER LYMNAEAS. 



FRAXIv COLLINS BAIv^R. 



The small forms of Lymntea, which have been included under the 

 names of humilis and desidiosa, have been little understood by Amer- 

 ican conchologists, at least two good species being included in 

 humilis. A recent somewhat exhaustive study of these small forms 

 has led the writer to conclusions diametrically opposed to those held 

 by Binney and Tryon and most subsequent students of fresh-water 

 mollusks. 



In pursuing these studies, the types of Say's and Lea's species in 

 Philadelphia and Washington have -been examined, and in addition 

 the collections of the Philadelphia Academy of Natural Sciences, 

 the Smithsonian Institution, Mr. Bryant Walker, Detroit, Michigan, 

 Mr. Henry Hemphill, San Diego, California, Mr. J. H. Ferriss, 

 Joliet, Illinois, and the Chicago Academy of Sciences have been 

 studied. My thanks are due to the above-named gentlemen for the 

 use of their collections, and also to Dr. W. H. Dall, Dr. H. A. 

 Pilsbry, Mr. Paul Bartsch and Mr. E. G. Vanatta, for much valu- 

 able assistance and kind criticism. 



Lymnsea humilis Say. 



Lyimiseus hnnnUs Say, Journ. Phil. Acad., II, p. 378, 1822. 

 Lymnea griffithiana Lea, Proc. Amer. Phil. Soc, II, p. 33, is-ll. 



