SPELERIUM. 177 



A plump little river shell of pleasing outline is 

 shown in Fig. 150, and is named Sphcerium sulcatum, 

 Ivam., Sphe'-ri-um sul-ka'-tum. The brown epider- 

 mis shows distinct lines of growth, and 

 Hj^ the shell is white internally. Its length is 

 half an inch or less. From California, 

 Oregon and Utah. These little mollusks 

 Fig. 150. are vei y active creatures, climbing about 

 on aquatic plants with great ease. 



Sphcerium patellum, Gld., pa-tel'-lum. Shell very 

 thin, resembling the last species but less robust, 

 smoother, one-fourth of an inch in length. Speci- 

 mens from Sonoma county, California. 



Sphcerium occidentale, Prime. Nearly circular in 

 outline, shell quite smooth and firm, robust, same 

 size as the last. Specimens from Weber Canon, Utah. 



Sphcerium, dentatum, Hald., den-ta'-tum. Hatchet- 

 shaped when viewed from the side, but bulged at the 

 umbones and heart-shaped at the ends. Epidermis 

 olive-green, glossy. One-fourth of an inch long. 

 From the Chehalis river. 



This completes our list of fresh- water bivalves, and 

 we go back to the ocean side once more, to search 

 among its sands and rocks for the mollusks which 

 have thus far escaped our notice. 



We will begin with one which scarcely differs in 

 shape from our last picture, Fig. 150. It is called 

 the Kelly-shell, Kellia suborbicularis, Mont., Kel'- 

 li-a sub-or-bic-u-la'-ris. The Kellias are little bivalve 

 mollusks which live in the ocean, where they hide 

 themselves in the sheltered places among the rocks, 

 or in other convenient retreats. This species has a 

 minute shell, thin and light colored. It is a south- 

 erner and hides among kelp roots. 



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