THE NAUTILUS. 141 



erately curved; scutum and scutellum distinct with slight projecting, 

 rounded angles at their terminations, the one at the scutum being 

 less marked in full-grown specimens; anterior and posterior ends 

 almost equally, obliquely truncated, especially in specimens not quite 

 mature, while in the adult the posterior end forms more a regular 

 curve from the beaks down to the rather low-situated rounded end; 

 surface with rather sharp, fine and crowded sulcations, usually some- 

 what coarser on the beaks, dull or with a slight gloss; a few strongly 

 marked lines of growth ; color grayish or whitish-brown in the young, 

 and the same in slightly marked marginal zones of older specimens 

 plumbeous in half grown, and reddish or brownish, or smoky-brown, 

 in the adult, with narrow, darker zones on the lines of growth; shell 

 thick, muscle insertions distinct, nacre white, almost porcellaneous, 

 with bluish zones corresponding with the lines of growth; hinge 

 strong, plate rather broad, cardinal teeth comparatively large, the 

 right strongly curved, emarginate at the free edge, its posterior part 

 thick, slightly to deeply grooved; t lie inferior in the left valve short, 

 curved, the superior shorter to longer than the inferior, moderately 

 posterior, oblique, little curved; lateral teeth strong, those of the left 

 valve with very high pointed cusps, ligament rather large, covered. 



Size : long. 15, alt. 11.;"), diarn. 9.5 mill. 

 Long. 14, alt. 11.5, diam. 9 mill. 



Habitat : Carp Lake, near Mackinaw City, Michigan, collected 

 by Mr. Bryant Walker. 



This is a remarkable Sphaerium. It stands near some large forms 

 of stamineum, yet by its shape, large diameter and very large beaks, 

 is different ; S. solidulum is more rounded in its outlines, less inflated, 

 its beaks are smaller, and the sulcation is coarser. In its surface 

 appearance, sulcation and color, our species resembles & simile, but 

 is much shorter, comparatively, its beaks are higher, the hinge mar- 

 gin is more curved and the hinge very much stronger. 



Sphcerium waikeri n. sp. Mussel small, well inflated, almost equi- 

 partite ; beaks little anterior, rather broad, rounded, not high, some- 

 what projecting over the hinge margin ; the latter rather short, little 

 curved ; scutum and scutellum scarcely marked, with slight, project- 

 ing rounded angles ; inferior margin slightly curved ; anterior end 

 well rounded, passing into the inferior without any indication of an 

 angle ; posterior slightly truncated obliquely, passing into the inferior 

 witli a low situated, rounded angle ; surface with very fine, some- 



