thyroidus = thyroid [latin]
Shell thin, fragile, convex, umbilicate; whorls five, obtusely wrinkled, or rather with equidistant, gradually elevated, obtuse lines, and spirally striate with minute, impressed lines; lip widely reflected, white and flate before, partially concealing the umbilicus; pillar lip furnished with a very oblique tooth.
Breadth four fifths to nine tenths of an inch.
This species very much resembles H. Albolabris of Nicholson's Encyc. Amer. Ed. but is umbilicated, and toothed on the pillar lip. It is much less common. This shell was indicated in the American Edition of Nicholson's Encylcopedia; but its characters were not laid down.
Original Description Citation:
Say T. (1817). Descriptions of new species of land and fresh water shells of the United States. Journal of the Academy of Natural Sciences of Philadelphia. 1 (6): 123-126.
Nature Serve Conservation Status: