106 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



Appalachian chain. It is also found fossil in the Post-pleiocene of the Missis- 

 sippi Valley. 



Animal uniform blackish slate-color over the whole upper surface, paler on 

 the posterior extremity and base ; collar grayish-white ; foot narrow, exceed- 

 ing in length twice the transverse diameter of the shell ; eye-peduncles long 

 and slender. There are well-marked lines running obliquely towards the cen- 

 tre of the base of the foot, where is an extremely narrow line, representing, no 

 doubt, the locomotive disk. The other characters of Zonites are present in the 

 species, such as the longitudinal furrows and caudal pore. 



Jaw (see Vol. I. PI. XII. Fig. 7) strongly arcuate, ends rounded ; anterior 

 surface striated ; concave margin with a well-developed median projection. 



Lingual dentition (PI. II. Fig. M). Teeth 38—1—38, with 14 laterals. 



The genital system (figured by Leidy, Vol. I. PI. XII. Figs. 4-7) is quite 

 complicated. The genital bladder is small, oval, on a long, delicate duct, from 

 about the middle of the length of which there is a connecting duct to the mid- 

 dle of the penis sac and a second duct to the apex of the dart sac. This last 

 organ is long, large at its junction with the vagina, tapering above, and fur- 

 nished below its apex with an accessor)-, short, delicate, cylindrical gland ter- 

 minating in a small pyriform bulb. The dart is loii£, delicate, strictly arrow- 

 shaped, with pointed, enlarged head and much thickened at the posterior 

 termination. The penis sac is stout, short, receiving at its apex the vas defe- 

 rens, on the commencement of which the retractor muscle is inserted. 



See remarks on the genitalia of Z. intertextus. 



Zonites intertextus, Binney. 1 

 Vol. III. PI. XXXVI. 



Shell perforated, subpyramidal ; epidermis yellowish horn-color; whorls 

 6 or 7, with numerous fine, oblique stria?, and very minute, spiral striae, inter- 

 secting each other ; outer whorl with a narrow, light-colored band, and an ill- 

 defined, brownish band below it; aperture rounded, a little transverse; peri- 

 stome thin, somewhat thickened within by a deposition of testaceous matter, its 

 columellar extremity slightly reflected at its junction with the base of the shell ; 

 perforation small, sometimes nearly obsolete ; base whiter than the upper sur- 

 face. Greater diameter 15, lesser 13| mill. ; height, 10 mill. 



Helix intertcxta, Binney, Bost. Journ. Nat. Hist., III. 413, PL XX. Fig. 2 (1840); 



Terr. Moll., II. 206, PL XXXVI. — Philipfi, Icon., II. 9, p. 5, PL VI. Fig. 



16. —Chemnitz, 2d ed., I. 208, PL XXXIII. Figs. 8 - 10. — Pfeiffer, Mon. 



Hel. Viv., I. 49. —Reeve, Con. Icon., 668 (1852). — Leidy, T. M. U. S., I. 



257, PL XII. Figs. 1-3 (1851) anat. — DeKay, N. Y. Moll., 38, PL III. 



Fig. 29(1843). — W. G. Binney, T. ML, IV. 96. 

 Mesomphix intertcxta, Tryon, Am. Journ. Conch., II. 254 (1866). 

 Hyalina intertcxta, W. G. Binney, L. & Fr.-W. Sh., I. 44 (I860). 



1 It has been suggested (Proc. Pliila. Ac. N. Sc. L875, 335) that this is the ligerus of 

 Say ; a theory entirely refuted by a reference to Say's description of ligerus. 



