110 cycladidj:. 



short side more rounded, so as to be scarcely distinguishable from 

 the European species. In general appearance it is very like Nucula 

 tenuis. 



Pisidium Adamsii.* 



Cjjdas nititla, Mighels, Bost. Joiirn. Nat. Hist. iv. 39, pi. 4, fig. 3 (1842); Pr. 1,48 



(1841). 

 Pisidium Adamsii, Prime, in Stimpson's Shells of New England, 16 (1851) ; Bost. Journ. 



Nat. Hist. vi. 352 ; Ann. of Lyceum, vii. 95. 



Shell sulvovate, full, oblique, inequilateral ; anterior side a little 

 longer, narrower, slightly produced at end ; posterior side broader, 

 somewhat sub-truncate at end, basal margin rounded ; 

 Fig. 417. beaks small, a little raised, approximate at apex ; sur- 

 face smooth, strise very delicate ; color light gray, in- 

 terior whitish ; hinge margin curved ; cardinal teeth 

 very small ; lateral teeth very distinct. Length, three 

 ^Eifia?ged.'' tenths of an inch ; breadth, twenty-four hundredths of 

 an inch ; width (height), two tentlis of an inch. 

 North America, at Norway in the State of Maine, and at Holly, 

 Oakland County, Michigan. 



A rare species. I have never seen any specimens but those in 

 the collection of the Boston Society and those in my own, all of 

 which came from Professor Adams, who discovered it with Dr. 



Mighels. The young is elliptical, ob- 

 liquely striate, and compressed. The so- 

 called Cijclas nitida, from Connecticut 

 and New Hampshire, is P. variabile. 

 Compared with P. variabile, this spe- 



P. Adamsii. . . , , • i n t 



cies IS larger, comparatively more deli- 

 cate, less oblique, less heavily striated, of a lighter color. It is 

 much more oblique and less elongated than P. abditum. It is more 

 oljlique, and more inflated than P. virginicmn ; it is also more del- 

 icate than that species (^Prime^. 



Pisidiura compressum.* 



Pisidium compressum, Prime, Proc. Bost. Soc. Nat. Hist. iv. 164 (1852) ; Ann. N. Y. Ly- 

 ceum, V. 219, pi. 6 ; vii. 97 ; Bost. Journ. Nat. Hist. vi. 356. 

 Cydns altilis, Anthony, in litt. 1847. 

 Pisidium compressum. Prime, Bost. Proc. iv. 164 (1851). 

 Pisidium altile, Anthony, Prime, Bost Journ. vi. 353 (1852), pi. xi. figs. 10-12. 



* See note, page 107. 



