40 THE NAUTILUS. 



well in ponds, rivers, brooklets and ditches, if only the water is 

 clean. If the bottom is of mud, it will be found clinging to sticks, 

 stone, dead leaves and submerged vegetation, climbing often nearly 

 to the surface of the water. It is a small shell usually less than 

 one-third of an inch long, and in color bright yellow, unless covered 

 with vegetable mould. The animal is pink, and shows through the 

 shell, so that the species may be recognized by its peculiar rosy 

 glint in the water. The shell is trapezoidal, slightly oblique, acutely 

 rounded in front, more elevated and truncate posteriorl5^ The 

 beaks are approximate at the apex and project forward. The ends 

 seem sharply pinched and there is a depression each side of the 

 beaks, giving the impression of a ridge from the apex to each 

 ventral end. This is the typical form and I have never seen it from 

 south of New Jersey, nor west of New York. 



Mr. H. F. Carpenter has described a Rhode Island shell as 

 Sphcerium deformis, which should be considered a variety of *S'. secure. 

 It is somewhat larger, more elongated, and the basal margin com- 

 pressed and distorted. From Adamsville, N. J., I have also many 

 specimens of Var. dejorviis, smaller than the Rhode Island shells, 

 but similarly twisted. 



While the typical S. secure is an eastern shell, the more western 

 states furnish some distinct varieties. From Traverse City, Mich., 

 comes a very yellow, elevated form, the animal of which is also yel- 

 low. This is probably the shell described by James Lewis as S. 

 croceuvi, and said to be found on gravel bottoms. This, however, 

 may be a condition, rather than a habit, as the same thing occurs 

 in the case o? S. secure at Readville, Mass., in a clean pond. 



From Fenton Co., Mich., I have a number of solid, globose, brown 

 shells, which were identified at the Philadelphia Academy of Sci- 

 ences as S. sphaericum Anth. They are thicker and more globular 

 than any New England specimens of S. secure, excepting those from 

 Readville, which are equally solid, with beaks more pointed, and in 

 color yellow. Even more closely resembling the Readville shell is 

 a form from Mercer Co., 111., of an olive green color. These forms 

 are liable to be confounded with >S'. occidentale Prime. The latter 

 is of the same size, but is perfectly oval, and the rounded beaks 

 hardly rise above the outline. *S'. partumemm is larger and more 

 lenticular, and *S'. truncatum is thinner, pellucid and less tumid. A 

 Kansas shell going the rounds as -S'. sphaericum, is another species, 

 much larger, and allied to S. contractmn and S. elevatum. 



