SUB-CLASS I ANTHOZOA—TETRACORALLA © 75 
Microcyclus, Meek and Worth. (Fig. 110). Like the preceding, but with 
only one septal fossula. Devonian ; North America. 
Family 3. Zaphrentidae. Milne-Edwards and Haime. 
Coralla simple, turbinate, conical, or cylindrical , septa numerous, exhiliting 
distinct bilateral symmetry in arrangement. Theca generally formed by fusion of 
septal ends. Tabulae completely developed ; dissepiments not very abundant in inter- 
septal locult. 
Streptelasma, Hall. Turbinate, often curved. Septa numerous (80-130), 
alternately long and short; the free edges of the longer septa are 
twisted together 
in the centre to 
form a_ pseudo- 
columella. = Tab- 
ulae few or 
absent. Posi- 
tion of the prin- 
cipal septum is 
recognisable — on 
the exterior by 
system of pin- 
nately diverging 
costal ridges. 
Common in Ordo- 
vician and Sil- 
urian. 
Zaphrentis, Raf. (Figs. 111-114). Simple, turbinate, or sub-cylindrical, 


Zaphrentis Canadensis, Bill. Hudson River group 
(Ordovician); Cineinnati, Ohio. 1/;. <A, Side view. 
B, Transverse section. (C, Longitudinal section. (h, Car- 
dinal septum; g, counter septum; s, alar septum.) 

Fic. 114. 

Fig. 112. Zaphrentis Enniskilleni, Nich. Carboniferous Lime- 
Zaphrentis cornucopiae, stone; Ireland. A, B, Transverse sections through re- 
Zaphrentis cornicula, Mich. Calice enlarged. spectively upper and lower’portions of calice. C, A long 
Lesueur. Devonian lime- Carboniferous Limestone; and two short septa united at the ends to form the wall. 
stone ; Ohio. Yournay, Belgium. D, Longitudinal section showing tabulae (after Nicholson). 
frequently elongated. Calice deep, with circular margin. Septa numerous, 
reaching to the centre; cardinal septum in a deep fossula. Tabulae numerous, 
somewhat irregular, and passing from side to side of the visceral chamber ; 
