MEMBRANIFORA AURITA. 159 



margin. The flatness and dull opaque look of 

 the surface of the zoarium are very characteristic. The 

 nodules are sometimes a conspicuous feature. 



MEMBRANIPORA AURITA, Hincks. 



Plate XXI. figs. 5, 6. 

 MEVBRANIPORA AURITA, Hincks, Ann. N. H. set. 4, rx. 213 (Sept. 1877). 



Zocecia ovate, somewhat expanded below, disposed with 

 great regularity in quincunx j area with a membra- 

 nous covering ; no calcareous lamina ; margin plain, 

 in young cells armed with four spines, of which one 

 is usually present in the adult, placed about halfway 

 down the side; immediately above each cell, or the 

 ovicell when present, two raised avicularia, one on each 

 side, with a pointed mandible usually directed upwards 

 and slightly outwards. Ocecia subglobose, partially 

 immersed, with a strong rib on the front, rising to a 

 point above and inclosing a triangular space. 



Colonies forming large subcircular patches, resembling 

 the most regular lace work. 



HABITAT. On stones and shells. 



LOCALITIES. Cornwall and Devon (T. H.) : Antrim 

 (Hyndman) : Northumberland (Alder). 



From M. Flemingii this species is distinguished by the 

 more regularly ovate form of its cell, the entire absence 

 of a calcareous lamina, the triangular figure on the front 

 of the ovicell, and the perfectly regular quincuncial 

 arrangement of the cells. The latter character is a very 

 marked one ; and in well developed specimens the species 

 may be at once recognized by it. 



Of the four spines which occur on young marginal cells 



