130 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



shell is smaller, so that the first two whorls are finer and more delicate ; and 

 the base is not so convex. The base of the shell is exceedingly like that of 

 Z. internus. 



It is the totality of the characters which makes up the species ; for indi- 

 viduals differ considerably in the height of the spire, the size of the umbilicus, 

 and in the degree of prominence of the teeth. One tooth is often wanting. 



The deposition of testaceous matter, thickening the shell at its aperture, occu- 

 pies about one fourth of the base, through which it is seen. The character of 

 the lamellar folds, within the aperture, resembles those of Sagda epistylium, Miil- 

 ler, in which species they are large and prominent. 



Jaw highly arcuate, ends attenuated, anterior surface smooth, cutting edge 

 with a well-developed median projection. 



The lingual membrane (PL III. Fig. K) has 30 1 30 teeth, with 10 per- 

 fect laterals. 



The genitalia have the two accessory glands to the dart sac, as in intertexius, 

 while supjyressus has but one. 



Zonites suppressus, SAY. 

 Vol. III. PL XXXVII. Fig. l. 



Shell convex depressed, thin, pellucid ; epidermis polished, yellowish horn- 

 color ; spire flat ; whorls 6, with crowded, minute, oblique striae ; suture im- 

 pressed, distinct ; aperture transverse, not expanded ; peristome simple, thin 

 at its edge, thickened within ; base rather convex, near the aperture opaque, 

 yellowish-white ; umbilicus small, but rounded and distinct in young shells, 

 obsolete or hardly apparent in older ones ; within the peristome are 1 or 

 lamelliform, elongated, oblique teeth. Greater diameter 5, lesser 4 mill. ; height, 

 2 mill. 



Helix suppressa, SAY, New Harm. Diss., II. 229 (1829); Descr. 14; BINNEY'S 

 ed. 36. BINNEY, Bost. Journ. Nat. Hist., III. 410, PI. XL Fig. 3; Terr. 

 Moll., II. 253, PL XXXVII. Fig. 1. DEKAY, N. Y. Moll., 38, PL III. Fig. 

 24 (1843). REEVE, Con. Icon. 723. W. G. BINNEY, Terr. Moll., IV. 122. 

 MORSE, Amer. Nat., I. 411, Fig. 25 (1867). PFEIFFER, Mon. Hel. Viv., IV. 

 153. LEIDY, anat. Terr. Moll., I. PL XII. Fig. VIII. 



Helix gularis, var. /3, PFEIFFER, in CHEMNITZ, ed. 2, etc. See Z. gularis. 



Gastrodonta suppressa, TRYON, Am. Journ. Conch., II. 258 (1866). 



Zonites suppressa, W. G. BINNEY, L. & Fr.-W. Sh., I. 293 (1869). GOULD and 

 BINNEY, Invert, of Mass., ed. 2, 454 (1870). 



I have considered this as a species of the Interior Region, which has passed 

 those limits ranging into the Northern and Southern Regions. I have actually 

 received it from New England to Florida and to Michigan. 



Animal : see p. 94, and Bost. Journ. of Nat. Hist., III. PL XI. Fig. 3. 



This shell does not correspond exactly with Say's description ; but I think 

 it is the same that he described under this name. Having received, from dif- 



