444 Annals of the Carnegie Museum. 



24. Musculium raymondi (J. G. Cooper). 



Spharium raymondi Cooper, Proc. Calif. Acad. Sciences (2), III, 1892, p. 74. 



Closely resembling M. ryckholti, and at least some forms ranged 

 under it may belong to that species. 



Habitat. — California (Sierra Nevada), Washington, British Colum- 

 bia. 



25. Musculium winkleyi Sterki. 



Musculium winkleyi Sterki, Nautilus, XXIII, 1909, p. 66. 

 Habitat. — Maine, Massachusetts. 

 Fossil. — Maine. 



26. Musculium securis (Prime). 



Cyclas securis Prime, Boston Proc, IV, 1851, p. 160. 

 Sphcerium securis Prime, Mon. Corb., 1865, p. 49. 



Very variable. The form cestivale (cf. The Nautilus, XXIII, p. 18) 

 is markedly different, and corresponding forms of most of the species 

 of Miisciiliiini have been seen. The designation is applicable to each 

 of them, since it is not a subspecific or varietal name. 



Habitat. — East of the Rocky Mountains, but apparently rare in 

 the South and wanting in the Gulf States; common in the Northeast; 

 South Carolina. 



Fossil.— "Ma.ine, Michigan. 



27. Musculium sphaericum (Anthony). 



Cyclas sphcBrica Anthony, Boston Proc, IV, 1852, p. 275. 

 Sphcerium s phcericum Prime, Mon. Corb., 1865, p. 50. 



Rather variable. It appears that M. splicer icuni is not specifically 

 distinct from M. securis Prime, although typical forms are noticeably 

 different from each other, they are inseparably and intricately con- 

 nected by intermediate forms. Both are decidedly variable, yet the 

 specimens from each habitat are fairly uniform; of both there are 

 forms with calyculate and with plain, rounded beaks, "cestivale.'' 



Habitat. — Northern Ohio and Indiana, Michigan, New York, New 

 England, more common in the western part of the area. 



28. Musculium sphaericum succineum var. nov. 



Mussel somewhat smaller, less inequipartite; beaks rather large 

 and full, the shell is translucent to transparent, of clear amber-color, 

 the surface glossy, with very fine slight striae, not scaly. 



