154 MEMB31ANIPOIIIDJ3. 



Range of Variation. There are slight differences in the 

 shape of the cell (the prevailing form being a very regular 

 oval) j and the spine at the bottom is sometimes wanting. 



Habitat. Stones from deep water. 



Locality. Ten or twelve miles south of Polperro, in 

 40 fathoms (T. H.). 



The avicularium is the striking feature of this species. 

 It is of very large size, suberect, and furnished with a 

 triangular mandible, which is much cui'ved towards the 

 tip. A very interesting peculiarity is the distinctness of 

 the area on which it is placed. It resembles very closely 

 that of the ordinary cells, being only slightly smaller and 

 having a similar granulated margin. The avicularium 

 rises out of the lower part of this inclosed cell-like area, 

 which it fills, the space above it being unoccupied and 

 destitute of membranous covering. The relation between 

 the appendage and the ordinary zooccium is very clearly 

 indicated in this species. 



I have a closely allied form from Singapore, which is 

 principally distinguished by the character of the a^dcu- 

 larium. 



Membranipora unicornis, Fleming. 

 Plate XX. fig. 4. 



Flustra unicornis, Flcm. Br. An. 536. 



Membkanipora membuanacea, Johnst. 13. Z. etl. 2, 328 (part.) ? 

 ?Lepralia squama, Dalycll, Eem. An. Scotl. ii. 70, pi. xxv. figs, 14, 15*. 

 Mejibranipora unicornis, Alder, North. Cat., Trans. Tynes. F, 0. iii. 14G, 



pi. viii. fig. 6. 

 Membranipora lineata, 5, forma unicornis, j8/3, staclium longius adultuui, 



Smift, CEfvers. K. Vet.-Ak. FGrli. 1867, 365 and 399, pi. xx. 



fig. 30. 



* Tliis and the preceding are very doubtful identifications. 



