. The Conchologists' exchange. Mollusks. BiFIDARIA AGNA n. Sp. The shell is rimate, cylindric, the last three whorls of about equal diameter, the summit very obtuse; surface nearly smooth; of a sperm- aceti-whitish color. There are 4| convex whorls, the last with a strong rounded crest behind the outer lip, rather close to it above, but being more oblique, it is further behind the lip at the base. Behind this crest the whorl is a little flattened laterally, and shows the lower palatal plica, though as a white spot. The aperture is brought forward nearly in line with the ventral convexity of th
. The Conchologists' exchange. Mollusks. BiFIDARIA AGNA n. Sp. The shell is rimate, cylindric, the last three whorls of about equal diameter, the summit very obtuse; surface nearly smooth; of a sperm- aceti-whitish color. There are 4| convex whorls, the last with a strong rounded crest behind the outer lip, rather close to it above, but being more oblique, it is further behind the lip at the base. Behind this crest the whorl is a little flattened laterally, and shows the lower palatal plica, though as a white spot. The aperture is brought forward nearly in line with the ventral convexity of the whorls. The peristome is thin, slightly expanded, strengthened a short distance within with a low callous rib. The parietal lamella appears distorted and angular in front view; seen from the base it is seen to consist of an angular and a parietal lamella, completely united inwardly. The columellar lamella is sinuated or bent and strongly developed. The basal fold is strong, arising on the callus but extending inward beyond it. The lower palatal fold is large and pliciform, more or less immersed, standing chiefly inward from the palatal callus. The upper palatal fold is much smaller, and stands rather near the lower, upon the palatal callus. There is a small or minute suprapalatal fold, also on the callus. Length , diam. 1 mm. Trinidad, Colorado, type no. 93052 A. N. S. P.; also Silver Lake, Kansas. This species resembles some forms of B. pentodon (Say), especially those from northern Alabama, in which the lower palatal fold is long. 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 Averell, William D. Philadelphia, Wm. D. Averell
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectmollusks, bookyear188
