284 GASTEKOPODES. 



same form as the Nautilmcs of the Tritonia Hombergii, 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. 



PLATE XL. 



FIG. 1. Tritonia, cervina, adult, upper surface. Cornicula, a, natural size. 



2. Another specimen, under surface, slightly enlarged. 



3. Corniculum, enlarged. 



4. Branchiae, enlarged. 



5. Younger specimen, enlarged. Back. Cornicula, a. Branchife, I. 



6. Another specimen, outline enlarged, upper surface. 



7. Under surface of the anterior part of fig. 6. 



8. Spawn. 



9. The same, enlarged. 



10. Nautiline. 



11. The same, contracted in the shell. 

 12, 13. Empty shells. 



