. Fresh-water biology. Freshwater biology. ioo8 FRESH-WATER BIOLOGY 141 (146) Male and female shells different; female shell with a decided infla- tion in the post-basal region, which is thinner than the rest of the shell, of different texture, often toothed, and usually radiately sculptured; hinge complete; marsupium occupying the posterior part of the gill only. Truncilla Rafinesque . 142 Four subgenera: 142, 143, 144, 145. 142 (143) Male shell smooth, no radial groove in front of the posterior ridge. Female with a high posterior ridge, posterior slope flattened. Subgenus Truncilla The
. Fresh-water biology. Freshwater biology. ioo8 FRESH-WATER BIOLOGY 141 (146) Male and female shells different; female shell with a decided infla- tion in the post-basal region, which is thinner than the rest of the shell, of different texture, often toothed, and usually radiately sculptured; hinge complete; marsupium occupying the posterior part of the gill only. Truncilla Rafinesque . 142 Four subgenera: 142, 143, 144, 145. 142 (143) Male shell smooth, no radial groove in front of the posterior ridge. Female with a high posterior ridge, posterior slope flattened. Subgenus Truncilla The type, T. friquctra Raf. (Fig. 1508), occurs from western Xew York to Nebraska and south to Kansas and northern Akibama. Five other species are found in Teruiessee and Fig. 1508. 143 (144) Male shell with a wide, radiating, shallow depression in front of the posterior ridge. Female with a small, rounded, well-defined radial post-basal swelling. Subgenus Scalcnaria Agassiz. The type, Truncilla sulcata Lea (Fig. 1509), ranges from the Tennessee River north to southern iVIichigan. Two other species occur in Tennessee and Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ward, Henry Baldwin, 1865-1945; Whipple, George Chandler, 1866-1924. joint author. New York, John Wiley & sons, inc. ; [etc. ,etc. ]
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
