NATURAL SCIENCES OF PHILADELPHIA. 165 



Z, demissus (pi. III., fig. 6, b is the 15th tooth) has 45 — 1 — 45 

 teeth, with 15 laterals. My specimen was one of the large East 

 Tennessee form, called Z. acerrus by Dr. Lewis. The typical form 

 fi'om near Mobile has, however, a perfectly similar dentition. 



Z. ligerus (pi. IIL, fig. 11,6 is the 18th tooth ; c, a profile of one 

 nearer the central line). Teeth 38 — 1 — 38 with 14 laterals. 



Z. intertextus (pi. III., fig. 8, h is from near the outer margin). 

 I find diflSculty in counting the teeth on one specimen examined 

 by me, but I believe there are 61 — 1 — 61. There are 12 perfect 

 laterals. Another specimen has 55 — 1 — 55 with 12 laterals 

 Z. sub2)lanus^ not examined. 



Z. inornatus (pi. II., fig. 5, fig. h is the 21st tooth). One spe- 

 cimen had 87 rows of 23—1—23 teeth. Another had 26—1—26. 

 Both had only two perfect laterals. 



Z. sculptilis (pi. IIL, fig. 2, b are extreme marginals) 40 — 1 — 40 

 teeth with 4 perfect laterals. 



Z. Elliotti (pi. IIL, fig. 5, b an extreme marginal) 32 — 1 — 32 

 teeth with 6 perfect laterals. 

 Z. cerinoideus^ not examined. 



Z. cellarius (pi. IL, fig. 2, one-half of one transverse line with 

 the median tooth) 14 — 1 — 14 teeth. There can hardlj' be said to 

 be one perfect lateral. For the other abnormal characters of this 

 lingual membrane see p. 163. The figures of dentition of the 

 foreign form (by Lehmann, Lindstrom, etc.) agree with mine. 

 Z. Whitneyi, not examined. 



Z. nitidus. See Lehmann, Lebenden Schneckcn, etc. p. 72, pi. 

 X., fig. 23, for description and figure of the European form. In a 

 specimen from Baldwin Count}'^, Alabama, furnished by Dr. E. R. 

 Showalter, I find 25—1—25 teeth with 5 laterals— (pi. XVIL, fig. 

 7, b is an extreme marginal.) Lehmann gives 28 — 1 — 28. 



The specimen examined had the dart-sac and dart described in 

 the European form. 



Z. arboreus. Morse gives 82 rows of 21 — 1 — 21 teeth each. 

 My specimen (pi. XYIL, fig. 4, b is an extreme marginal) has 

 about 16 — 1 — 16 with 5 perfect laterals. There ai*e distinct side 

 cusps as well as cutting points to the central and lateral teeth. 



Z. viridulus (pi. XYIL, fig. 6). Morse gives 54 rows of 

 27 — 1 — 27 teeth each. I have figured the central and first lateral, 

 with one extreme marginal tooth, drawn from a specimen furnished 

 me by Mr. Allen of Orono, Maine. I find three lateral teeth. 



