POLYPIFERA, Ae 
Fossin PoLyPIFERA. 
As we proceed in our investigations, the impossibility of 
rigidly adhering to a zoological classification based on the 
_ structure of organs, of which but few, if any, traces exist in 
the mineral kingdom, becomes more and more apparent ; the 
durable skeletons or polyparia being the only materials from 
which the paleontologist can gather information, relating to 
the physiology of the extinct coral-animals which swarmed 
in the ancient seas, and whose petrified remains constitute 
a large proportion of the secondary and palseozoic calcareous 
rocks, 
Numerous fossil genera have been established by various 
authors from the external form of the polyparium, or the 
disposition and structure of the cells; but a slight attention 
to this department of paleeontology will disclose corals which 
differ essentially from the typical forms, and new genera and 
species will require to be added to the already extended 
catalogue. The few genera selected for the present work, 
will convey a general idea of the nature of this class of 
fossils. ‘'I'o ascertain the names of the species he may collect, 
the student must refer to works especially devoted to the 
illustration of the corals of particular rocks; as for example, 
those of the British Cretaceous deposits in the monographs 
of the Paleontological Society ; of the Paleozoic in Sil. Syst. 
and in Prof. Sedgwick’s Synopsis of the Classification of the 
Brit. Pal. Foss. ; of the Mountain Limestone in Prof. Phillips’s 
work; and those of Ireland in Col. Portlock’s Geological 
Memoirs. Those of the paleeozoic rocks of New York, are 
illustrated in Prof. James Hall’s splendid work on the Geology 
of that State. 
The fossil zoophytes included in this section present in- 
numerable varieties of form and structure, but agree in the 
