204 



FOSSIL ACTINOZOA. 



the Tubulose genus Aulopora, from which they can only be 

 separated by the presence of infundibuliform tabulae. The 



Fig. 92. Syringopora retiformis. 

 A Silurian Tabulate Coral. 



Fig. 93.Syringo}:ora verticillaUt. 

 Silurian. 



Fig. 94. Syringopora Dalmani. 

 Silurian. 



Fig. 95. Syringopora compacta. 

 Silurian. 



species of the genus are widely distributed in the Silurian, 

 Devonian, and Carboniferous formations. The remaining 

 genera of the Halysitidce have little 

 general interest ; but it may be men- 

 tioned that one (Fletcheria) is said to 

 range as high as the Trias. With 

 this exception, the family seems to 

 die out in the Carboniferous. The 

 curious Silurian genus, Tetradium, 

 widely distributed in North America, 

 may also be noted here, as affording 

 a link between the Halysitidce and the Chcetetidce. 



Fig. 96. Aulopora serpens. 

 Devonian. 



IV. TUBULOSA. 



This is a small group of corals, including the genera Aulo- 

 pora and Cladochonus (Pyrgia}, to which, perhaps, Stomato- 

 pora should be added. The corallum may be simple or com- 

 pound (fig. 96), the corallites being pyriform, or trumpet- 



