15i MEMBRANIPORID^E. 



HANOE OF VARIATION. There are slight differences in the 

 shape of the cell (the prevailing form l>eing a very regular 

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



HABITAT. Stones from deep water. 



LOCALITY. Ten or twelve miles south of Polperro, in 

 10 fathoms (T. II.). 



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 curved 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 zooecium is very clearly 

 indicated in this species. 



I have a closely allied form from Singapore, which is 

 principally distinguished by the character of the avicu- 

 larium. 



MEMBRANIPORA UNICORNIS, Fleming. 



Plate XX. fig. 4. 



FLUSTRA UNICORNIS, Flem. Br. An. 536. 



MEMBRANH-ORA MEMBRANACEA, Johiist. B. Z. ed. 2, 328 (part.) ? 

 ?LEPRALIA SQUAMA, Dalyell, Bern. An. Scotl. ii. 79, pi. xxv. figs. 14, 15*. 

 MI.MIUIAM I'iiuA UNICORNIS, Alder, North. Cat., Trims. Tynes. F. C. iii. 14(i, 



pi. viii. fig. 6. 

 Al I.MUKAM I'MKA LINEATA, 5, forma UNICORNIS, /3)3, stadium longius adultum, 



Smitt, (Efvers. K. Vct.-Ak. Forh. 18G7, 365 and 3'Jt), pi. xx 



fig. 30. 



* This and the preceding are vcrj doubtful identification- 



