304 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



depressed, the last convex below, with a prominent, acute carina above ; aper- 

 ture oblique, subtriangular, narrowed by a tongue-shaped, arcuately entering 

 tooth on the parietal wall ; peristome thin, broadly expanded, its inner edge 

 with a heavy thickening of white callus, its right portion with a stout, erect 

 denticle, its basal portion straight, dilated, reflected, with a long, lamellar, less 

 prominent denticle. Greater diameter 26, lesser 22 mill.; height, 11 mill. 



Helix obstricta, Say, Journ. Phila. Acad., II. 154(1821); Binnet's ed. 17. — 



Pfeiffer, Mod. Hel. Viv., I. 317. — Reeve, Con. Icon., No. 683(1852).— 



W. G. Binney, Terr. Moll., IV. 57 ; L. & Fr.-W. Sh., I. 125 (1869). — Bland, 



Ann. N. Y. Lye, VII. 446. 

 Helix palliata, var. a, Say, Journ. Phila. Acad., II. 152; Binney' s ed. 16. — 



Var. a, b, DeKay, N. Y. Moll., 33, PI. II. Fig. 16 (1843). — Var. Binney, 



Terr. Moll., II. 137, PL XV. 

 Helix appressa, var. Deshayes in Fer. (in plate, not in text). 

 Helicodonta denotata, var., Ferussac, Tab. Syst., 38; Hist., PL L. A, Fig. 7, no 



descr. 

 Caracolla helicoides, Lea, Trans. Am. Phil. Soc, IV. 103, PL XV. Fig. 34 ; Obs. 



I. 113 (1834). 

 Helix Caroliniensis, Lea, Trans. Am. Phil. Soc, IV. 108, PL XV. Fig. 33 ; Obs. 



I. 112 (1834). 

 Xolotrema obstricta Tryon, Am. Journ. Conch., III. 49 (1867). 



A post-Pleiocene species (Natchez Bluff), now found in the Interior Region, 

 in Ohio, Indiana, Tennessee, Georgia, South Carolina. 



T. obstricta differs from T. palliata in the following particulars : the epi- 

 dermis is free from " tuberculous prominences," but has raised spiral lines be- 

 tween the costae, on the upper and lower surface of the shell. It bas elevated 

 rigid, distant costae, the whorls are subexserted and acutely carinated, the 

 carina of the upper whorls compressed, and overlapping the sutures, as in 

 Patula Cumberlandiana. The umbilicus, as in the most carinated form of T. 

 palliata, is not always entirely covered by the reflected peristome. 



Var. J3. — Whorls subexserted, carina less acute and prominent, partially 

 obsolete behind the aperture, not covering the sutures. Greater diameter 24, 

 lesser 19 mill.; height, 8 mill. (5 whorls.) Columbus, Georgia. This variety 

 connects T. Caroliniensis with T. obstricta, and is generally found in cabinets 

 under the former name. 



Var. y. — Whorls more convex, the last obtusely angulated in front of, but 

 very little behind the aperture. Greater diameter 21, lesser 17 mill.; height, 

 1\ mill. (5 whorls.) South Carolina. This is the typical T. Caroliniensis, hold- 

 ing precisely the same relation to obstricta as palliata to palliata var. y. Also 

 found in Tennessee and Georgia- 

 Jaw as usual; over 10 ribs. 



Lingual membrane (PL VII. Fig. P) has 33—1—33 teeth; 10 perfect later- 

 als ; very like T. palliata. My figures are drawn from that part of the lingual 



