136 THE NAUTILUS. 



Margarita helicina Fah. Reported not uncommon between tides 

 around Victoria; not yet discovered at Maple Bay. 



Solariella peramabilis Carpenter and Solariella cidaris Carpenter. 

 I have a few nice examples from dredgings in or near Departure 

 Bay, the latter though, only from channels outside the bay. 



Note. While I have been able to do much more collecting at 

 Maple Bay liian at Departure Bay, dredging has as yet been 

 attempted only at (he latter locality. 



" Errata." NAUTILI'S, Vol. xxiv, page 114, line 10, read " tiny" 

 instead o!' " fine." 



BPB..ffiKIIDJ, OLD AND HEW, IV. 



BY V. STERKI. 



Pisidium overi, n. sp. Mussel rather small, oblique, with the ante- 

 rior part somewhat longer, medium to well inflated; superior margin 

 short, nearly .straight, posterior subtruncate to rounded, inferior well 

 curved ; supero-anterior slope beginning with an angle, close to beaks, 

 rather long, straight to slightly curved ; anterior end situated well 

 below the median line, rounded angular; beaks rather small, rounded; 

 surface dullish to somewhat glossy, with very fine subregular striae; 

 shell thin, translucent, nearly colorless to pale corneous; hinge me- 

 dium stout, plate narrow; cardinal teeth rather long, moderately 

 curved to nearly straight, the right not, or little thicker in its poste- 

 rior part, left anterior with its apex rounded to somewhat pointed in 

 old specimens; ligament and resilium rather short and slight. 



Long. 3.5, alt. 3, diam. 2.4 mm. (100 : 91 : 68). , 



Long. 3.3, alt. 2.7, diam. 2.1 mm. (100 : 82 : 64). 



Hab. : Clear Lake, Deuel Co., S. Dakota, collected by Mr. W. H. 

 Over, in several lots, in 1906 and 1908; types No. 5752 and corre- 

 sponding with those in Mr. Over's collection, in whose honor the 

 species was named (in 1906). Apparently the same Pisidium is from 

 Cannon Lake, Rice Co., Minnesota, collected by Mr. L. E. Daniels 

 in 1905 (No. 5595); the two specimens in the collection are some- 

 what larger and more inflated, with the beaks higher. 



P. overt somewhat resembles walkeri St. in shape and appearance, 



