152 Rev. T. Hincks's Contributions towards 



occurs on M. curvirostris, mihi ; and it is not uncommon 

 amongst the species with a membranous front wall. 



Memhranipora (Caleschara) denticulata, MacGillivray*. 

 (PI. VIII. fig. 2.) 



Zoarium foliaceous, with the cells in two layers placed back 

 to back, or incrusting. Zocecia arched above, widening about 

 the middle, and contracted below ; margin smooth, sometimes 

 traversed by a brown line, inner side of the cell-wall 

 granular ; area occupying the whole front of the cell, the 

 lower one third filled in by a granulated calcareous plate ; a 

 transparent membranous wall extending over the entire area, 

 including the calcareous plate, the oral valve being placed at 

 the very top of it ; from the centre of the upper edge of the 

 lamina rises abroad calcareous process (also granulated), which 

 extends to about one third the length of the aperture from the 

 top, where it sends off two lateral branches to the wall of the 

 cell, forming in this way a foramen on each side, the inner 

 edges of which are denticulate ; the upper margin of the 

 process is slightly thickened, and shuts off a semicircular 

 space above, corresponding with the operculum in the true 

 front w^all ; at the bottom of each cell one or sometimes two 

 rather large smooth nodules. Ooecium wide, little projecting, 

 incorporated with the cell above, both the ovicelligerous cell 

 and the one above it of unusual size {MacG.). 



Lac. Victoria [MacGilUvray) : off Curtis Island, Bass's 

 Straits, on shell, forming a brown subcircular patch [Capt. 

 Cawne Warren). 



MacGillivray places this species among the Escharidse 

 (Busk), simply, it would seem, on the ground of its erect 

 habit. It has, in truth, no real affinity with this family as 

 constituted by Busk. The depressed area, the elevated 

 margins, and the membranous front wall show that its place 

 is amongst the Membraniporida}. Nor is there any sufficient 

 ground, in my judgment, for referring it to a new genus. The 

 peculiarity on which MacGillivray founds his Caleschara 

 (" front calcareous, except a small part anteriorly, which is 

 membranous ") is, I believe, quite insignificant. I venture 

 to think that he has misinterpreted the structure of the 

 zooecium, probably owing to the imperfect condition of the 

 specimens which came under his notice. The " front " of his 

 description is not the true front wall of the cell, but merely a 

 calcareous upgrowth from the edge of the lamina (strictly 



* 'Prodromus of the Zoology of Victoria,' decade v., by Fred. M'Coy, 

 r.R.S. ; ' Polyzoa/ by P. H. MacGillivray, p. 45, pi. xhiii. fig. 8. 



