162 MEMBRAXIPORID^E. 



just referred, the scale and general character of the 

 zooecia are very dissimilar in the two forms. 



I am not acquainted with any other species with which 

 the present can be confounded. M. irregularis, D'Orb., 

 with which Busk compares it, exhibits a totally different 

 type of cell. 



b. With a calcareous lamina. 

 MEMBRANIPORA FLEMINGII, Busk. 



Plate XXI. figs. 1-3. 



FLUSTRA MEMBKANACEA, Muller, Zool. Dan. iii. 63, pi. civii. figs. 1, 2. 

 MEMBRANIPORA MEMBRANACEA (part.), Johnst. Br. Zooph. ed. 2, 328 (not 



pi. Ivi. fig. 7). 



FLCSTRA TUBERCULATA, Johnst. B. Z. ed. 1, 289. 

 AMPHIBLESTRUM MEMBRANACEUM, Gray, B.M. Kad. 110. 

 MEMBRANIPORA FLEMINGII, Busk, B.M. Cat. ii. 58, pi. Imiv. figs. 3, 4, 5 



(not pi. civ. figs. 2, 3, 4) : Alder, Hincks, HeUer, Ac. 

 MEMBRANIPORA FLEMINOII, forma TRIFOLIUM (part.), Smitt, 1. c.,Krit. Fort. 



iii. 367 and 405, pi. rs. figs. 37 & 40. 



Zooecia ovate, more or less produced below; area con- 

 tracted above, much expanded and elevated below, filled 

 in for about a third of its length by a calcareous granular 

 lamina ; aperture trifoliate ; margin much raised, crena- 

 ted ; oral spines six (in young cells usually eight) two, 

 very tall and slender, placed at the top, and two, much 

 stouter, on each side below them, the foremost of those 

 on one side often enormously developed, and forming a 

 long, flattened, scimitar-like appendage, which is articu- 

 lated to a short tubular process on the margin. Avicu- 

 laria one on each side below the area, raised, with acute 

 mandible directed upwards and outwards when the ovi- 

 cell is present, but usually downwards when it is absent ; 

 sometimes a single central avicularium, placed trans- 



