140 Prof. W. King on Pleurodictyum problematicum. 



of innumerable minute cells, each being inhabited by a single 

 Bryozoon. If it were possible for the intestinal canal of every 

 animal in a LepraUa to be preserved, a vermiform appendage 

 ought to occur in every cell. 



We have now arrived at the great difficulty which besets us 

 in considering our fossil to belong to the class Bryozoaria; for 

 as there is only one appendage to all its cells, it is evident that 

 each one cannot have been tenanted by a single Bryozoon. But 

 let us again consider the Zoanthic affinities of Pleurodictyum. 

 AYhy may it not have been inhabited by a Bryozoic form orga- 

 nized after the Zoanthic type ? In short, why may not its occu- 

 pant have been a Zoanthoid Bryozoon ? According to this view, 

 Pleurodictyum, although consisting of a number of cells, be- 

 longed to a simple individual ; and it necessarily follows that its 

 cells, instead of being aggregated corallites, were merely cham- 

 bers corresponding with the interseptal s])aces or loculi charac- 

 teristic of the lamelliferous corals, particularly those in which 

 these parts are formed by confluent plates, as in most species of 

 Stephanophyllia. The cells were probably receptacles for the 

 generative organs ; and they possibly indicate the existence of a 

 number of concentric circles of tentacles similar to. those sur- 

 rounding the orifice of an ordinary Actinia. 



In Pleurodictijum, the varying number of cells or chambers, 

 which is altogether dependent on its size, is not opposed to the 

 suggestion just made ; since the tentacles in Actinia and some 

 allied genera are well known to increase in number as the polyp 

 increases in size. 



It would be unwise to specialize too much in an hypothetical 

 restoration of the animal that belonged to our fossil ; but I can- 

 not refrain from hazarding the conjecture that the chambers 

 were surmounted by the stomach. It is highly improbable that 

 the vermiform appendage comprised both the stomach and in- 

 testine, like the alimentary apparatus in Echinidce, in which, it 

 must be understood, the large visceral cavity allows full room for 

 the necessary dilatation of the gastric portion ; because in the 

 fossil the whole appendage w'as so hemmed in by the substance 

 of the cell-walls as to render impossible an increase of any por- 

 tion of it by repletion, supposing any such portion served as a 

 stomach. I am therefore led to consider the vermiform append- 

 age as being the cast of a tubular chamber which enclosed only 

 the intestinal canal, a view which, it will be observed, is in exact 

 accordance with my conjecture as to the cells being inferior in 

 position to the stomach. Perhaps the constriction I noticed at 

 one of the terminations of the appendage indicates the com- 

 mencement of the rectum. 



In conclusion, it remains for me to observe, that if the view 



