DIASTOPORIOE. 115 



The true characters of the species are apparent only in a few specimens, in which the 

 centre of the disc exhibits the proper openings of the cells, which are disposed much in 

 the same way as in much- worn and thickened specimens of Patinclla patina. One pecu- 

 liarity of P. prolir/era is the great width, thickness, and rotundity of the cellular border, 

 in which also the alveolar orifices of the cells are peculiar, from their large size and 

 elongated, rhomboid shape, and by which peculiarity even small fragments of the species 

 may often be distinguished without difficulty. 



The discs are frequently much contorted, of which an instance is represented in 

 PI. XX, fig. 3. 



Genus 9. DISCOPORELLA, Gray. 



Polyzoario sessili vel adnato, disciformi convexo vel subconico rarissime depresso. 

 Cellulis horizontalibus plerumque in lineas radiantibus vel irregulariter dispositis, orificio 

 denticulato vel emarginato ; superficie interstitial! caucellata. 



Polyzoarium sessile or adnate ; discoid, centre usually elevated or subconical, rarely 

 depressed ; tubes horizontal, usually disposed in radiating lines, or irregularly ; mouth 

 toothed or emarginate ; intertubular surface cancellous. 



DISCOPOKELLA, Gray, List Brit. Rad., Suppl., p. 138. 



DISCOPORA (pars), Fleming (not Lamarck) ; Busk, Brit. Cyclop., art. " Polyzoa," p. 16. 



MADREPORA (pars), Fabr. ; Esper. 



TUBULIPORA (pars), M. Edwards; Johnston; auct. 



1. D. HISPIDA, Johnst. (?) PI. XVIII, fig. 5. 



Adnata ; cellulis in lineis radiantibus dispositis, orificio bi- tridenticulato. 

 Polyzoarium adnate ; cells in radiating lines, with a bi- tridenticulate mouth. 



DISCOPORA HISPIDA, Fleming; Blainv., Hassall ; Couch. 



TUBDLIPORA HISPIDA, Johnst. 



ORBICULUS (?), Lamarck. 



Habitat. C. Crag, S. Wood; (Recent], Britain. 



This is but doubtfully identified with the recent form, although the presumption is very 

 strong that it is the same with one of the probably several species confounded under the 

 appellation. 



