142 HISTORICAL’ PALZONTOLOGY. 
the many forms of these, the species of Cyathophyllum, Helio- 
phyllum (fig. 82), Zaphrentis (fig. 81), and Cystiphyllum (fig. 80), 
are perhaps those most abundantly represented—none of these 
genera, however, except He/iophyllum, being peculiar to the 
Devonian period. There are also numerous compound Ru- 
gose corals, such as species of Lridophyllum, Diphyphyl- 
lum, Syringopora, Phillipsastrea, and some of the forms of 
Cyathophyllum and Crepidophyllum (fig. 83). Some of these 
compound corals attain a very large size, and form of them- 
‘s SSH » 
Fig. 83.—Portion of a mass of Crepidophyllum Archiact, of the natural size. 
Hamilton Formation, Canada. (After Billings.) 
selves regular beds, which have an analogy, at any rate, with 
existing coral-reefs, though there are grounds for believing that 
these ancient types differed from the modern reef-builders in 
being inhabitants of deep water. ‘The ‘“‘’Tabulate Corals” are 
hardly less abundant in the Devonian rocks than the Augosa ; 
and being invariably compound, they hardly yield to the latter 
in the dimensions of the aggregations which they sometimes 
form. 
The commonest, and at the same time the largest, of these 
are the ‘“‘honeycomb corals,” forming the genus /avosites 
(figs. 84, 85), which derive both their vernacular and their 
technical names from their great likeness to masses of petrified 
honeycomb. ‘The most abundant species are /avosites Goth- 
landica and F. hemispherica, both here figured, which form 
masses sometimes not less than two or three feet in diameter. 
Whilst avosctes has acquired a popular name by its honey- 
combed appearance, the resemblance of AZichelinia to a fossil- 
