THE NAUTILUS. 5 



and G. speciosa, both of which, on comparison of specimens, are seen 

 to be much more cylindrical. The latter differs in being decidedly 

 smoother below, even glabrous, while G. lheringi is striated to the 

 base. The body-whorl is strongly swollen and convex, and the nar- 

 row moniliferous subsutural border is particularly distinct and ele- 

 gant. 



NEW PISIDIA, AND SOME GENERAL NOTES. 



BY DR. V. STERKI. 



Pis. imbecille n. sp. Mussel minute, ovoid-oblong in outline, 

 rather inflated ; superior and inferior margins moderately curved, 

 posterior slightly truncated obliquely outward, rounded below, antero- 

 superior slightly curved or almost straight (oblique), anterior end 

 rounded ; beaks somewhat posterior, broad and low, slightly raised 

 above the hinge margin in the adult ; color pale yellowish horn to 

 whitish ; surface with very flue striation and a few slightly marked 

 lines of growth, and with a slight waxy gloss ; shell thin, hinge very 

 fine and plate quite narrow ; cardinal teeth very small, thin, or al- 

 most obsolete, lateral teeth small, the outer ones of the right valve 

 scarcely visible ; ligament fine. 



Size: long. 2.3, alt. 1.8, diam. 1.3 mill. 



Habitat : Byer's Trout Pond, and Button Lake, Kent Co., Mich., 

 collected by Dr. K. J. Kirkland. 



This is a well characterized species, not nearly related with any 

 other, and can not be mistaken for mature specimens of any one. 

 But it has much resemblance with very young examples of Pis. 

 variabile Pr., of the same size, and it takes good care to discern 

 them. — Our species will doubtless be found in other places ; in Byer's 

 Pond Dr. K. collected over four hundred specimens, and twenty- 

 five in Button Lake. The name has been derived from its small 

 size, thin shell, low, broad beaks, and some similarity in shape with 

 Anodonta imbecillis Say. 



Pis. peraltum, n. sp. Mussel of moderate size, somewhat oblique, 

 very high, much inflated, beaks large, full and prominent ; hinge 

 margin strongly curved; posterior part, behind the beaks, very short, 

 the margin high, slightly to distinctly truncated, passing into the 

 well rounded inferior, with a wide, regular curve; antero-superior 



