HELIOLITID.E. 



335 



septa of Heliopora. For these reasons, amongst others, Heliolites 

 and its relations may be placed, provisionally at any rate, in a 

 separate family. 



The recent Heliopora ccerulea is found in the Indian and Pacific 

 oceans, and fossil species of the genus are found in the Cretaceous 

 and Eocene deposits. The imperfectly known genus Polytremacis, 

 from the Cretaceous rocks, appears to be closely related to 

 Heliopora. 



Heliolitid.e. 



This family comprises a number of Palaeozoic corals, of which 

 the type is the widely distributed and abundant genus Heliolites it- 

 self, and is closely similar to the preceding group in its general 

 characters. The corallum (fig. 216) is composite, and consists of 

 two sets of tubes, of different sizes, of which the larger ("auto- 



Fig. 216. — A, Small colony of Heliolites interstinctus, Linn., of the natural size; b, Small por- 

 tion of the surface of the same, magnified, showing the autopores {a) and the mouths of the 

 siphonopores (6) ; c, Vertical section of the same, enlarged, showing the tabulate autopores (a), 

 and the similarly tabulate siphonopores (£). (Original.) 



pores ") are, as a rule, completely separated from one another by the 

 intervention of the smaller (" siphonopores "). Both sets of tubes 

 are provided with tabulae (fig. 216, c), and the autopores are fur- 

 nished with lamellar, or rarely spiniform, septa, the number of 

 which is almost invariably twelve in each corallite. In some cases 

 the septa unite centrally to form a reticulate pseudocolumella. 

 The siphonopores increase principally by fission, though partly by 

 intermural gemmation, while the autopores are produced by 



