SUB-CLASS I HY DROZOA—TUBULARIAE ae 
extend continuously through a number of lamellae. Both lamellae and _ pillars 
consist of minutely tubulated tissue, the tubules of which are radial in arrange- 
ment. Centre frequently occupied by a foreign body. Cambridge Greensand 
(Cenomanian). 
The genera Parkeria and Loftusia were originally described as agglutinated 
Foraminifera ; but they are manifestly very closely allied to £/lipsactinia and 
Sphaeractinia. 
Porosphaera, Steinm. (Fig. 196). Globular masses of the size of peas or 
hazel-nuts, frequently growing around some foreign body, and composed of 
anastomosing calcareous fibres which are penetrated by 
numerous radial tubules ; the latter open on the surface in the 
form of large pores, around which radial or stellate furrows 
(astrorhizae) are sometimes grouped. Upper Cretaceous. 

Fic. 196. 
Porosphaera globu- 
laris, Phill. sp. Upper 
Cretaceous; Riigen. 
A, Skeleton, natural 
size ; 1, Cavity origin- 
ally occupied by 
Tniee TOR. foreign body. B, Trans- 
verse section showing 
Loftusia Persica, Brady. Eocene; Persia. A, Specimen cut open to show general radial tubes of gastro- 

structure, natural size (after Brady). 6, Section showing two lamellae and inter- pores, 2/; (after Stein- 
laminar filling, greatly enlarged. mann). 
Stoliczkaria, Duncan. Trias; Karakoram and Balkan Mountains. 
Heterastridium, Reuss. (Syringosphaeria, Duncan).  Spheroidal, nodular 
bodies of considerable size, composed of slender, anastomosing, and more or 
less distinctly radial calcareous fibres. Skeleton comparatively dense, but 
perforated by two series of zodidal tubes appearing superficially as pores. The 
apertures of the larger tubes are round, those of the smaller stellate, and are 
surrounded by radial furrows. Alpine Trias. 
Appendix to the Hydrocorallinae and Tubulariae. 
Stromatoporoidea. Nicholson and Murie. 
Closely allied to the Hydrocorallinae and Hydractinia are the extinet Stromato- 
poroidea, which combine in many respects the characters pertaining to both of 
the above-named groups, but whose exact position in the zoological system 
remains as yet uncertain. During the Palaeozoic era, to which they are con- 
fined, the Stromatoporoids were important geological agents, whole beds of 
limestone being often essentially constituted of their remains. In the Mesozoic 
era they are replaced by very closely allied forms of Hydractinia, which in all 
probability represent their immediate descendants. 
The Stromatoporoids secrete hemispherical, globular, nodular, or horizontally 
expanded skeletons, which are sometimes encrusting, sometimes attached by a 
short basal peduncle, and are covered on the under side with concentrically 
