MACIIOCYCLIS. 



405 



Fig, 607. 



ITelix lincata, Say, Journ. riiila Acad. i. 18 (1817) ; ii. 273 (1824) ; Nidi. Encyc. 3d cd. 

 iv. (1819) ; Binnky's cd. 7, 24. — Binney, Bost. Joiirn. Nat. Hist. iii. 43G, pi. 22, 

 fig. 6 (1840) ; Terr. Moll. ii. 2G1, i)l. 48, tig. 1. — De Kay, N. Y. Moll. 44 (1843). 

 — Gould, liiv. 170, fig. 1()3 (1841 ).— Adams, Vermont Moll. 161 (1842).— 

 Fercssac, Tab. 8yst. 44 ; Hist. pi. 7'.), lig. 1. — Desiiayes in Fkii. i. 80. — Ciie.m- 

 NiTZ, 2d cd. ii. 203, t. 101, figs. 13 - l.'i. — Peeiffeu, Mon. Hel. Viv. i. 184.— 

 Keeve, Con. Icon. 724 (1852) — W. G. Binney, Terr. Moll. iv. 123. — Mouse, 

 Amcr. Nat. i. 546, fig. 44 (1807). 



Plaiiorhls paral/eliis, Say ? Journ. Pliila. Acad. ii. 164 (1821) ; cd. Binney, 63. 



Ilclicodiscas linenta, Mor.se, Journ. Portl. Soc. i. 25, figs. 61, 62; pi. 2, fig. 3; pi. 8, fig. 

 63 (1864). — '1'rvon, Aai, Journ. Concii. ii. 264, pi. 4, fig. 60 (1866). 



Shell minute, discoidal, fiat above, concave beneath, greenish ; 

 wliorls about four, flat above, higher than broad, sep- 

 arated l)y a distinctly impressed suture, covered with 

 lunnerous, parallel, raised, revolving' lines; olherwise 

 smooth ; aperture narrow, semi-lunar ; lip sinij)le and 

 thin ; umbilicus wide and deep, exhiltiting each volu- 

 tion to the ape.x;. Within the a})erture, on the exter- 

 nal wall, are placed two pairs of white conical teeth, 

 the first pair in sight on looking into the aperture, 

 the other more remote, and seen only through the 

 semi-transparent shell. Diameter, one eighth of an 

 inch, usually less. 



Animal whitish, transparent, thi'cad-like. 



It has been noticed, for the most part, under the bark, or in the 

 interstices, of rotten wood ; sometimes under stones and leaves in 

 damp places. Inhabits all of Eastern North America, having been 

 found i'rom Gaspe to Texas ; also on the Rio Chama, New Mexico. 



At first sight one Avould be disposed to call this shell a Plcm.orbis 

 rather than a Helix. Perhaps it is the P. para/lclns of Say. Its 

 wheel-shaped form, greenish color, revolving raised lines, and sin- 

 gular teeth, are characters which cannot be mistaken. One pair of 

 these teeth may always be found and seen ; and in one instance Dr. 

 Binney noticed even a third pair still farther within the whorl. 



Genus ]?IACKOCYCL,BS, Bv.ck. 18.37. 



Shell thin, widely umbilicated, depressed, striate or wrinkled, 

 color uniform; whorls four and a half to five, the last broad, de- 

 pressed, moderatf^ly dcflexed in front, aperture obliquely ovate ; 

 peristome somewhat thickened or expanded, the margins approx- 

 imating, the basal shortly reflexed. 



