222 MICROPORELLID^. 



A remarkable change is produced in the appearance of 

 the zoarium by the progress of the calcification. At a very 

 short distance from the top of the branches the boundaries 

 of the cells and many of their characteristic features are 

 sometimes obliterated by the enormous overgrowth of 

 calcareous matter; the whole surface, with the exception 

 of a small space below the orifice, is overlaid with a thick 

 crust, which rises into numerous wart-like prominences, 

 and is traversed by irregular grooves, and presents, even 

 to the naked eye, a strikingly rugose appearance. In the 

 older portions little but the orifice is visible of the original 

 cell ; even the avicularium is almost buried beneath the 

 stony envelope. In this condition the species well deserves 

 the name which Mr. Peach has given it. 



Genus CHORIZOPORA. 



Der. From x'^pi'i^i to separate, and iropos, a passage or opening. 



Flustra (sp.), Audoiiin. 



Lepralia (sp.), Johnston : Busk : &c. 



MoLLiA (part.), D'Orbigny. 



Generic Character. — Zocecia more or less distant, 

 connected by a tubidar network; the orifice semicircular, 

 with the inferior margin entire ; the special pore wanting. 



This genus agrees with Microporella in having a 

 semicircular orifice with the lower lip straight and 

 entire, but diff'ers from it and the rest of the family 

 in being destitute of the special pore on the front wall. 

 In other respects it is peculiar. The cells are separated 

 from one another, but are connected at intervals by 

 tubular extensions of the wall (Plate XXXII. fig. 4). 

 In our British form the tubes sometimes pass imme- 



