1910.] 



NATURAL SCIENCES OF PHILADELPHIA. 



671 



Fig. 5. — P. bermudensis Pils. 



A. havanensis Pfr. is larger and more elliptical. Type in the collection 

 of the Acad. Nat. Sci. Phila., No. 100,338. 



Paludestrina bermudensis n. sp. Pilsbry. Fig 5. 



"The shell is perforate, turrite, the spire regularly tapering to the 

 small but obtuse apex; thin but mod- 

 erately strong, white under a thin yellow- 

 ish cuticle, in life generally black from 

 ferrous incrustation. Whorls six. strongly 

 convex, the first one planorboid above. 

 Aperture ovate, the peristome thin, con- 

 tinuous, appressed to the preceding- 

 whorl for a short distance, above the 

 perforation. 



" Length 4.9, diam. 2.1 mm.; length of 

 aperture 1.9 mm. 



" Ditch in Pembroke Marsh, near Hamil- 

 ton, Bermuda. Type No. 100,340, Acad. 



Nat. Sci. Phila., collected by E. G. and E. E. Vanatta, March 2, 1910. 

 Also a pond near the entrance to Harrington Sound (Owen Bryant) 

 and Paynter's Vale (C. Abbott Davis). 



"The measurements of other specimens are as follows: 



"Alt. 6.8, diam. 3 mm., whorls 6f (largest specimen). 

 " 4.5 " 2.3 " " 5^ (broad phase). 



" 4.9, " 2.1 " " 6 (slender phase). 



"It was found in very copious quantity, and seems to be generally 

 distributed where suitable water occurs. It differs from Paludestrina 

 nickliniana (Lea) and its large form attenuata (Hald.) by the con- 

 spicuously more minute apical whorls. The denticulation of the 

 central and lateral teeth also is finer. The whorls of P. bermudensis 

 are more convex than in P. tenuipes (Couper)." (Pilsbry). 



Pisidium volutabundum n. sp. Fig. 6. 



Shell equivalve, suborbicular, umbones moderately prominent, 

 thin, horn color, superior margin nearly straight, anterior margin 

 subtruncate, inferior margin arcuate, posterior margin convex. Sur- 

 face finely striate with irregular lines of growth. Hinge arcuate, 

 narrow, ligament scar concave with a slight longitudinal ridge in the 

 center. The right valve with one large cardinal and two laterals at 

 each end, the lower ones the largest. The left valve provided with 

 two cardinals the lower recurved and a little anterior, a very heavy 



