nsiDiuM. 113 



Pisidium ferrugineum.* 



Pisiditim /erruijinpum, Pkime, Proc. Bost. Hoc. Nat. Hist. iv. 162 (1852); Bost. Joiirn. 

 Nat. Hist. vi. 362, pi. 12, tigs. 8, 9, 10; Ann. N. Y. Lye. vii 98. 



Shell small, rounded-oval, globose, slightly inequilateral ; anterior 

 side somewliat produced ; margins rounded ; beaks 

 tuljercular at aj)ex, very distant ; surface smooth ; ^'°" ^^' 



epidermis light yellow ; hinge-margin rounded ; car- 

 dinal teeth large, separate, anterior tooth more prom- 

 inent ; lateral teeth distinct. Length, seventeen hun- 

 dredths of an inch ; breadth, thirteen hundredths 

 of an inch ; width, eleven hundredths of an inch. p. /frn,s:ineum. 



^ Enlarged. 



North America, in the States of Maine and New 



X Ol'K. Yia-, 424. 



Remarkable for the elevation of its beaks, which stand 

 forth on the upper portion of the shell in the shape of 

 large tubercles, which are generally coated with some P-fimigi. 

 dark ferruginous substance. It differs from P. ahditum 

 ill being smaller, more inflated, not so elongated, and more equilat- 

 eral. 



One of our most common species, found usually in company with 

 P. variabile and P. ventricosum (^Prime}. 



Pisidium abditum.* 



Pisidium ahditum, Haldejian, Proc. Acad. Nat. So. Phila i. 5.3 (1841). 



Cyclas minor, C. B. Adams, Bost. Proc. i. 48 (1841). 



Pisidium teneJlum, Gould, Agassiz's Lake Superior 245, (1848). 



Pisidium obscurum, Prime, Bost. Proc. iv. 161 (1851). 



Pisidium rubellum. Prime, loc. sup. cit. iv. 16.3 (1851). 



Pisidium minus, Stimpson, Moll. New England, 16 (1851). 



Pisiiliiim Kuitzi, Prime, Bost. Proc. iv. 162 (1851). 



Pisidium zonatum, Prime, loc. sup. cit. iv. 162 (1851). 



Pisidium regulare, Prime, Bost. Journ. vi. 363 (1852), pi. 12, figs. 11, 12. 



Pisidium mtatuin. Prime, loc. sup. cit. vi. 365 (1852), pi. 12, figs. 20-22. 



Pisidium arciiatum. Prime, loc. sup cit. vi. 364 (1852), pi. 12, figs. 14-16. 



Pisum abditum, Deshayes, Brit. Mus. Cat. 282 (1854). 



Pisiim minus, Deshayes, loc. sup. cit. 281 (1854). 



Pisidium resivtnm, Ingalls, in litt. 1855. 



Pisidium ruhrum, Lewis, in litt. 1855. 



Pisidium plenum, Lewis, in litt. 1855. 



Musculium abditum, Adams, Rec. Gen. ii. 451 (1858). 



Musculium minus, Adams, loc. sup. cit. ii. 451 (1858). 



Musculium rubellum, Ada.ms, loc. sup. cit. ii. 452 (1858). 



* See note, page 107. 

 8 



