NATURAL SCIENCES OF PHILADELPHIA. 211 
vinals of H. thyroides, for instance, would hardly have been ex- 
pected, so utterly different are they from those of albolabris. 
Again, we should hardly have expected to find such a difference 
in the same subgenus, as the presence and absence of side cutting 
points on the central and first lateral teeth. 
I will now give the count of teeth in the several species. 
Helix major, not examined. 
Helix albolabris (pl. XI., fig. 1). Outer laterals have distinct 
side cusps as well as cutting points. ‘Teeth 44—1—44, with about 
12 laterals. The inner cutting points of fig. b should be bifid. 
Helix divesta, not examined. 
Helix multilineata (pl. XII., fig. 6), 42—1—42; 12 laterals. 
Helix Pennsylvanica (pl. XVIII., fig. 3), 40—1—40 ; 13 perfect 
laterals. Morse counted 120 rows of 39—1—39 teeth. | 
Helix Mitchelliana (pl. XVIII., fig. 5), 49—1—49; 18 laterals. 
Outer laterals have side cusps and cutting points. 
Helix elevata (pl. XII., fig. 1), about 45—1—45; 17 laterals. 
Helix Clarki (pl. X1., fig. 6), 85—1—35, with 15 laterals. 
Helix Christyi, not examined. 
Helix exoleta (pl. X1., fig.7) has 56—1—56 ; 11 perfect laterals, 
but even the 8th tooth shows a decided modification in form. 
Helix Wetherbyi (pl. XI., fig. 2) has 85—1—35; 12 laterals. 
Helix Wheatleyi (pl. XVIII., fig. 1) has 67—1—67, with over 
12 laterals. 
Helix dentifera (pl. XII., fig. 8) has 82—1—82 teeth, with 15 
laterals. 
Helix Roémeri (pl. XI., fig. 3) has 85—1—35 teeth, with 12 
laterals. 
Helix thyroides (pl. XVIII., fig. 2) has 60—1—60, with 11 
laterals. 
Helix clausa (pl. XII., fig. 7) has 41—1—41, with about 11 
perfect laterals. 
Helix Columbiana (pl. XII., fig. 2) has 33-133 teeth ; 15 
perfect laterals. 
Helix Downieana (pl. X1., fig. 4) has 35—-1—35 teeth, with 12 
laterals. The side cusps and cutting points are visible on the 
second lateral tooth. 
- Helix Lawi, not observed. 
_ Heliz Mobiliana. The true species, from Baldwin County, 
