MADREPORARIA PERFORATA. 



307 



themselves in any prominent manner till the Tertiary period is 

 reached, and they have attained their maximum at the present day. 



In the following brief summary of the characters and distribution 

 in time of the leading groups of the Perforate Madreporarians, it 

 will be best to take first the three recent families above mentioned. 



Family 1. Enpsammidce. — In this family the corallum may be sim- 

 ple or compound, the wall of the corallites being perforated, while 



A B 



Fig. 18S. — Palceacis cyclostotna, from the Carboniferous rocks of Scotland, a, Upper surface 

 of a colony enlarged twice ; b, Vertical section of the corallum, showing the reticulated struc- 

 ture of the skeleton, enlarged. (Original.) 



the principal septa may be entire and imperforate. The smaller 

 septa are, however, usually perforate, and in other cases all the septa 

 are trabecular. There is a limited development of endothecal tis- 

 sue, the interseptal loculi thus remaining more or less open. This 

 family is principally Tertiary and Recent, but the genus Calostylis is 

 Silurian, and there are also Cretaceous types {Step ha nop hy I li a, &c.) 



A B C 



Fig. 189. — Calostylis Andersoiii, from the Wenlock Limestone of Shropshire, a, A broken 

 specimen, enlarged slightly ; b, Transverse section, enlarged five times ; c, Vertical section, 

 similarly enlarged, showing the thick wall and the trabecular character of the septa. (Original.) 



It is clear, therefore, that our knowledge of the past history of the 

 family is extremely imperfect. 



The most ancient type of this family is the genus Calostylis, first 

 described by Lindstrom from the Wenlock Limestone of Gotland, but 

 occurring also in deposits of the same age in Britain. In this genus the 



