lOi TERRESTRIAL AIR-BREATHING MOLLUSKS. 



the " Boston Journal," which represents an entirely smooth shell. Pfeiffer also 

 quotes H. rii/a, DeKay, as a synonyme of ktv'igata. It seems rather to be the 

 young of some other species. 



Reeve figured liemgatus under the name of inornata^ describing it as striate 

 in the text. 



Much confusion regarding the species of this group has existed also among 

 American collectors, who have depended for the names of their shells on their 

 friends rather than on the study of descriptions. 



The species under consideration is at once distinguished from all the others 

 of the group by the fact of its being the only one furnished with striaj on the 

 upper surface. 



Jaw as usual in the genus. 



Zonites hevigatus (PI. II. Fig. F) is peculiar in having no cutting points to 

 the side cusps of the central teeth on its lingual membrane, and no perfect 

 lateral teeth (see p. 97). I found in one specimen 28 rows of 19 — 1 — 19 teeth. 

 Another specimen had 17 — 1 — 17 teeth. One half of one transverse row with 

 the central tooth is figured on PI. II. Fig. F. This peculiar dentition distin- 

 guishes the species from all its allies. 



The ovary is short, and vagina long. The genital bladder with its duct 

 forms a short cylindrical sac-like organ, opening near the base of the vagina 

 and tapering at the apex. Tlie penis sac is long, cylindrical, larger at its 

 apex, wliere it receives the vas deferens. At its base the penis sac has its 

 opening into the vagina with a short stout organ {d, s) with rounded apex 

 where a retractor muscle (r) seems to be attached. This organ may be a dart 

 sac or some form of prostate gland (PI. XI. Fig. E). 



Zonites demissus, Binney. 

 Vol. III. PI. XLII. Fig. 1. 



Shell perforated, depressed-convex ; epidermis yellowish horn-color, shining ; 

 whorls 6, with minute lines of gi-owth ; spire obtuse ; suture impressed ; body- 

 whorl expanding very little towards the aperture ; apertiu'e transverse, not 

 large, slightly oblique ; a white, testaceous deposit within ; peristome thin, 

 acute ; base rather flat, smooth ; perforation very small ; umbilical region a 

 little impressed. Greater diameter 11|^, lesser 10^ mill. ; height, 6 mill. 



Helix demissa, Binney, Bost. Journ. Nat. Hist., IV. 361, PI. XVI. Fig. 16 

 (1843); Terr. Moll., II. 232, PI. XLII. Fig. 1 (1851). —Pfeiffer, Mon. Hel. 

 Viv., I. 58 ; IV. 48.— Reeve, Con. Icon., No. 1491. — W. G. Binney, Terr. 

 Moll, IV. 116. 



MesompMx demissa, Tryon, Am. Journ. Conch., II. 255 (1866). 



Hyalina demissa, W. G. Binney, L. & Fr.-AV. Sh., I. 45 (1869). 



Zonites acerra, Lewis, Proc. Ac. N. Sc. Phila. 1875, 335. 



The centre of distribution of this species seems to be the Cumberland Sub- 

 region, where it has attained its finest growth. From here it ranges into West- 



