THE NAUTILUS. 29 
Thirteen species were obtained, and may be noted as follows: 
1. ’CrrcinaRIA CONCAVA Say. A number of large and typical 
specimens of this species were collected and kept alive for a long 
time on the writer’sdesk. On May 18th two individuals were noted 
in coitu, the coitus lasting from 8 o’clock A. M. to 6 o’clock P. M. 
During this time both animals were perfectly quiet, the eye pedun- 
cles and tentacles drawn into the head and the foot contracted to 
form a rounded oval. During the coitus the heart, which normally 
beats about 75 times per minute, was reduced to 19 very slow and 
long beats. The foot of the snail taking the active part was partly 
covered by the passive snail, and the former’s head was slightly 
lifted. The specimens measured about 15 mill. in greatest diameter. 
2. VITREA ARBOREA Say. A few specimens of this species were 
obtained under and in rotting logs. All were perfectly typical. 
3. OMPHALINA FULIGINOSA Griffith. The specimens obtained 
were rather dark in color and about half grown, the umbilicus wide 
and deep. 
4. PoLyGyRA (MESODON) ALBOLABRIS Say. But a single speci- 
men of this species was obtained alive, and that was very large, 
measuring 34 mill. in greatest diameter. The animal was kept in 
captivity for several weeks, and was more active than any of the 
other species of Mesodon that the writer has studied. It wasstarted 
at the bottom of a book case door four feet long and reached the top 
in about half an hour. The examination of the lingual membrane 
gave 45-1-44 teeth with ten perfect laterals. In this membrane the 
38th tooth was abnormal in having three well formed cusps of equal 
size, instead of a bifid inner cusp. 
5. PotyGyra (Mrsopon) ExOLETA Binney. Several typical 
specimens of this species were collected, among which there was one 
without the parietal tooth. The lingual membrane of one specimen 
gave 47-1-47 teeth with eight perfect laterals. The marginals 
were very variable, some being with and some without side cusps. 
It is probable that several teeth were torn away from this mem- 
brane, although there could not have been the normal number given 
by Binney, 60-1-60. 
6. PotyGyra (MEsODON) THYROIDES Say. All specimens were 
of the normal form. 
‘For the change in names of several of the genera and species here listed, 
see Pilsbry, Proc. Phila. Acad., 1894--97, where adequate reasons are given. 
