CYCLOSTOMATA. 62 1 



mouths of which are commonly disposed in groups of different size 

 and form, separated by porous or imperforate interspaces. The 

 genera Frondipora and Fasciadipora (Fungella) are both represented 

 by species which range from the Chalk to the present day, and there 

 are several other genera which are found in the Cretaceous or 

 Tertiary rocks. Of the Tertiary forms the most interesting is the 

 genus Fascicularia (3Leandropo?'a), which is exceedingly abundant 

 in the Red Crag (Pliocene) of Britain. In this genus (fig. 464) the 



Fig. 464. — Fascimlaria (M<zaiidrofiora) ccrcbriformis. Tertiary. 



polyzoary is more or less massive, generally globose, and often of 

 large size, composed of long calcareous tubes arranged in bundles, 

 the tubes of each bundle being in contact, and the bundles being 

 enclosed laterally in a calcareous membrane. The bundles diverge 

 from the base of the colony, and may be connected by horizontal 

 and concentric plates, or may be confluent by their sides and thus 

 give rise to vertical convoluted laminae. The tubes are destitute of 

 "rays," but exhibit horizontal "tabulae," and have minutely porous 

 walls. In the common Fascicularia aurantium of the Red Crag the 

 tubes open on the surface in sinuous anastomosing ridges, while in 

 the allied F tubipora, of the same formation, they open on rounded 

 eminences. 



The family of the Heteroporidtz is in some important respects 

 related to that of the Lichenoporidce, and comprises the genera 

 Heteropora and Heteroporella. The polyzoary in this family may 

 be erect and branched, or may be encrusting ; and is composed of 

 tubular zocecia which are interspersed among similarly tubular but 

 somewhat smaller "cancelli," all the tubes being in close contact 

 throughout, and the mouths of the zocecia not projecting above the 

 general surface. The walls of the zocecia and interstitial tubes or 

 cancelli are penetrated by minute tubules, which place contiguous 

 cells in communication (fig. 456) ; and in some species at any rate, 

 delicate radiating spines (" rays ") are developed. There is also 

 generally a larger or smaller number of " closing-plates " or " tabulae," 

 which are principally developed in the deeper parts of the colony. 

 In the genus Heteropora itself, the colony is erect and branched, the 

 tubes being vertical in the centre of the branches, but bending out- 



