. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 162 TERRESTRIAL AIR-BREATHING MOLLUSKS. Fig. 72. Foot not much exceeding in length the diameter of the shell, and terminating in a broad, obtuse, and flat extremity. A light marginal line runs along the edge of the foot from the head to tlie posterior part, those of the two sides meetinij in an acute ansrle. Variety: head and neck blackish-brown, eye-peduncles blackish, foot brown- ish, base dirty white. In a single instance the whole animal was entirely black. The animal of the ribbed form of alternata found
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 162 TERRESTRIAL AIR-BREATHING MOLLUSKS. Fig. 72. Foot not much exceeding in length the diameter of the shell, and terminating in a broad, obtuse, and flat extremity. A light marginal line runs along the edge of the foot from the head to tlie posterior part, those of the two sides meetinij in an acute ansrle. Variety: head and neck blackish-brown, eye-peduncles blackish, foot brown- ish, base dirty white. In a single instance the whole animal was entirely black. The animal of the ribbed form of alternata found at University Place, Franklin County, Tennessee, by Bishop Elliott, resembles in length, etc., Ctim- berlandiana; it is dark slate-color on top of head and eye-peduncles; dirty white on bottom of foot; remainder dark orange. The variation of color ranges from pale straw to dark reddish-brown, in each extreme being sometimes uniform. In outline the variation ranges from depressed to very globose. In sculpturing it varies greatly. A comparatively smooth variety, with a shin- ing, somewhat translucent epidermis, has been noticed in New York, by Mr. Bland, under the name of var. Fergusoni. A form with stronger striffi and well-developed carina is figured in Fig. 71. The coarsely striated form, wliich I presume to be //. mordax, is figured also (Fig. 72). This is considered by Mr. Bland to be a variety of Cumberlandiana. I have received it from Eastern Tennessee and Vir- ginia. I have also given a figure (Fig. 73) of the magnified surface of a strongly ribbed form from North Carolina, and a view (Fig. 74) of a strongly ribbed form from the Post-pleiocene. In New England this is perhaps the most common species of the jrcnus. It abounds in the forests, and is not uncommon in the open country in moist situations, where it can find shelter under logs and stumps. It seems to be more gregarious than other species ; at any rate, numbers are more frequently found in the same retreat. It do
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