200 FOSSIL ACTINOZOA. 



corallites, which are often enveloped basally by a common 

 epitheca, and have their walls pierced by one or more rows 

 of regular apertures (" mural pores "). The septa are absent 

 or spiniform, and the tabulae, though usually complete, are 

 sometimes imperfect (Emmonsia, fig. 86). The genus Michc- 

 linia (fig. 87) possesses a corallum very like that of the 

 massive forms of Fawsites ; but the epitheca is often fur- 

 nished with root -like prolongations, the tabulae are arched 

 and somewhat vesicular, and the mural pores are numerous 

 and usually irregularly distributed. The genus is essentially 

 Devonian and Carboniferous. 



Fig. 87. Michelinia convexa (D'Orbigny). Devonian. 



In the genus Alveolites, again, palaeontologists usually in- 

 clude a number of branching or massive corals, which agree 

 with Favbsites in most respects, but which have short oblique 

 corallites, with sub-triangular or crescentic calices (fig. 88). 

 Nearly allied to Alveolites are the genera Cce-nites and Pachy- 

 pora, of the Silurian and Devonian. Of the remaining 

 genera of the Favositidce, Striatopora (fig. 89), of the Silu- 

 rian and Devonian, is remarkable for the form of its calices ; 

 and Koninckia is specially noticeable as being found in strata 

 as young as the Cretaceous. 



2. Chcetetidce. In this family we have a great number of 

 Palaeozoic corals, in which there is a compound corallum 



