220 MILLEPORA ALCICORNIS. 



different kinds of sheaths of the Sertiilarians and of the Campannla- 

 rians, and especially in the great development of the horn-like net- 

 work forming the base of a Hydractinia colony, and the hmestone 

 floors deposited by the base of the animal of Millepora is only an 

 extreme case for Acalephs, similar to the solid radiating partitions of 

 the Madrepores among Polyps. 



Tortugas, Fla. (L. Agassiz). 



Cat. No. 382, Tortugas, Fla., March, 1858, L. Agassiz. 



