CYCLOSTOMATA. 



627 



each branch having from two to five rows of cells. The species of Phyl- 

 lopora range from the Ordovician rocks to the Permian. Lastly, in the 

 Carboniferous genus Go?iiocladia the branches anastomose as in Phyl- 

 lopora, but they are keeled on both sides, and there are three or four rows 

 of cells on each side of the median keel on the poriferous side. 



The family of the Acanthocladidce comprises a number of Palae- 

 ozoic Polyzoa which are in many respects allied to the Fe?iestellidce. 



Fig. 471. — Carboniferous Polyzoa. <z, Fragment of Polypora dendroides, of the natural size — 

 Ireland ; a', Small portion of the sau.e, enlarged to show the cells ; b, Pinnatopora (Glauconome) 

 puldu:rri7na, a fragment, of the natural size — Ireland ; />', Portion of the same, enlarged ; c, 

 The central screw -like axis of Archimedes Wortheni, of the natural size — Carboniferous, 

 America ; </, Portion of the exterior of the frond of the same, enlarged ; c", Portion of the 

 interior of the frond of the same, showing the mouths of the cells, enlarged. (After M'Coy and 

 Hall.) 



In this family the polyzoary is " poriferous on one side only, den- 

 droid, pinnate, or forming fenestrated expansions, and consisting of 

 strong central stems and numerous smaller lateral branches which 

 proceed from their opposite margins. The lateral branches are free, 

 or may unite (in the fenestrate genera) with those of the adjacent 

 branches. Non-poriferous dissepiments are absent " (Ulrich). 



