168 PROCEEDINGS OF THE ACADEMY OF 
Z. capsella (pl. IIl., fig. 4), 25—1—25 teeth, with 3 perfect 
laterals, and one transition tooth. 
Z. fulvus. Morse gives 80 rows of 18—1—18 teeth, with 7 
laterals. The specimen examined by me (from Orono, Maine) 
has 30—1—30 teeth with 8 perfect laterals. The difference in the 
marginals is unusual for two individuals of the same species. 
The peculiarity of the lingual is the bifurcation of all the mar- 
ginal teeth. On pl. XVILI., fig. 5, I have drawn one central with 
its adjacent lateral, and one marginal extracted from a Maine 
Specimen. 
By the bifurcation of the marginals this species is allied to Z. 
Gundlachi, which, however, has even some of its marginals tricus- 
pid, and tricuspid laterals. 
The American form here under consideration was described by 
Mr. Say under the name chersina. Judging from its shell alone, 
it seems identical with the European Z. fulvus. It has thus been 
considered one of the circumpolar species common to the three 
continents. My confidence of this identity is now shaken by a 
study of the description and figure by Lehmann (Lebenden 
Schnecken, etc., p. 79, pl. X., fig. 24), of the dentition of the Eu- 
ropean Z. fulvus. He gives 86-100 rows of 25—1—25 teeth, the 
first two laterals he makes tricuspid, while they are only bicuspid 
in our form. The marginals appear to be bifid. The question of 
identity must therefore be considered as still open. 
Z. Fabricit, not examined. 
Z. Gundlach (pl. III., fig. 10, b, shows two marginals from two 
adjoining transverse rows), 23—1—23 teeth, with 4 perfect laterals. 
This lingual is peculiar in having its marginals bluntly bifid, as 
in Nanina and Vitrina. Some of the marginals are even trifid. 
The laterals are also tricuspid. 
Z. Stearnsi, not examined. 
Z. gularis (pl. III., fig. 1), has 30—1—30 teeth, with 10 perfect 
laterals. 
4. suppressus (pl. XVI., fig. 2, b are marginals from near the 
edge of the membrane). Teeth 30—1—30, with 8 perfect laterals. 
Z. lasmodon (pl. III., fig. 7, b the smaller figure shows the 38th 
tooth). Teeth 41—1—41, with 9 perfect laterals. 
Z. significans (pl. XVII., fig. 10). 16—1—16, with 2 perfect 
laterals. : 
