T1IK NAUTILUS. 43 



lines of growth, rather dull and microscopically rugulose ; color 

 grayish white to yellowish horn, in some specimens slightly plumbe- 

 ous around the beaks ; shell moderately thick, nacre white, muscle 

 insertions distinct but not impressed ; hinge rather stout, plate, rather 

 broad; right cardinal tooth strongly curved over a deep excavation, 

 its posterior part thickened and grooved to bifid, the left anterior 

 strongly curved and rather massive, placed rather high up on the 

 plate, the posterior oblique, curved, its anterior part reaching to or 

 over the middle of the anterior ; lateral teeth stout, the cusps rather 

 short, the outer ones in the right valve rather small but well formed ; 

 ligament strong. 



Size : Long. 4.5, alt. 3.9, diam. 2.6 mill. 



Habitat: Marsh from a spring on Lake James, Steuben Co., In- 

 diana, numerous specimens collected by Mr. L. E. Daniels, of the 

 Indiana Geological Survey, in whose honor the species is named. 

 During the season of 1902 Mr. Daniels has collected many and in- 

 teresting Pisidia and Sphasria, especially in northern Indiana, a 

 section from which very little had been known. 



The present species has some resemblance with typical Pis. 

 strengii. but in the latter species the o.utlines are more angular, the 

 beaks narrower and more prominent and rounded, the striation is 

 finer, and the hinge slighter. Pis. daniehi is of special interest. 

 From the features of the surface, the beaks and the hinge, there is 

 no doubt but that it ranges under the same group with P. com- 

 pressurn, kirkhmdi, cructatum, fallax, etc., although the rounded out- 

 lines, the low beaks, and the moderate and regular convexity would 

 suggest rather the contrary at first sight. Young specimens, how- 

 ever, have an unmistakable similarity of the outlines with those of 

 Pis. compression Pr. In some of the specimens the beaks are 

 broader, and the depression and ridge are less marked or almost ob- 

 solete, just as it is with certain forms of Pis. compressutn. 



Pisidium obtusale C. Pfr. 



At the same place as the preceding Mr. Daniels has collected 

 numerous specimens which are distinct from all North American 

 species described, but exactly like Pis. abtusale from several places 

 of Europe, and appear to be identical with that species. They are 

 rather large and almost globular; long. 3.6, alt. 3.1, diam. 2.6 mill. 

 It is to be expected that the same will be found also at other places. 



