284 GASTEROPODES. 
same form as the Nautilines of the Tritonia Hombergit, above described, as 
mere specks : they likewise traversed the water rapidly. The shell seemed 
to be rather longer than that of the other, less incurved, and with scarcely 
more than a notch for an orifice. It is of extreme transparence, without 
any visible connection with the body of the animal it contains. The in-. 
ternal organs of the included animal, the two spots about the same site 
as of the tentacula of the adult, and the activity of the cilia, are all con- 
spicuous. 
For eight days the animals were quite entire and transparent, hav- 
ing undergone no alteration, but afterwards they contracted and disap- 
peared, leaving their shells at the bottom of the vessel as before. 
Perhaps this species feeds on the Sertularia abietina. 
This animal is not common. 
PuateE XL. 
Fic. 1. Tritonia cervina, adult, upper surface. Cornicula, @, natural size. 
. Another specimen, under surface, slightly enlarged. 
. Corniculum, enlarged. 
. Branchie, enlarged. 
. Younger specimen, enlarged. Back. Cornicula, a. Branchie, 6. 
. Another specimen, outline enlarged, upper surface. 
. Under surface of the anterior part of fig. 6. 
. Spawn. 
Oo COT SO OS OO PD 
. The same, enlarged. 
10. Nautiline. 
11. The same, contracted in the shell. 
12, 13. Empty shells. 
