REPORT ON THE POLYZOA. 19 



have been separated on that account. These rooting processes are divided by vibices, and 

 in each division thus formed there is usually a small triangular avicularium, and also a few- 

 large pores. In section this process is seen to be composed of large chambers, the avicula- 

 rian muscles only occupying a small part. The structure of the radical process of 

 Rete/pora colnmnifera is identical. I have not seen Retepora imperati from the Medi- 

 terranean, and if it had been common at Naples should have expected it to come into my 

 hands. 



Retepora gigantea, Busk (PL III. fig. 6). 



Retepora gigantea, Busk, Zool. Chall. Exp., part xxx. p. 114, pi. xxvi. fig. 7. 



The dorsal surface has numerous small semicircular avicularia, and there are also 

 similar ones on the front. 



Retepora lata. Busk (PI. III. figs. 9, 40). 



Retepora lata, Busk, Zool. Chall. Exp., part xxx. p. 115, pi. xxvii. fig. 1. 



I have for some years possessed two large specimens of this from Algoa Bay, but 

 could not decipher the structure, as calcareous growth seems to have taken place over the 

 anterior surface, obliterating the characters. The opercula and mandibles at once prove 

 it to be Retepora lata ; besides which, the extremely small fenestrse are tho same, and I 

 have also been able to see an ovicell with the vertical fissure. Besides the anterior 

 triangular avicularia, there are small oval ones ; the dorsal surface is areolated, and some- 

 times throws out calcareous radical processes. Sections show that in the thick dorsal 

 walls there are the numerous empty spaces mentioned (p. 21) as occurring commonly in 

 Retepora. 



Retepora porcellana, MacGillivray. 



Retepora porcellana, MacGillivray, Trans. Roy. See. Vict., vol. ix., 1869, p. 140; op. cit., vol. 



xix. p. 289, pL ii. fig. 9; Zool. of Vict., dec. x. p. 15 ; pi. 94, fig. 8 ; 



pi. 95, figs. 1-6. 

 Retepora rohusta, Hincks, Ann. and Mag. Nat. Hist., ser. 5, vol. i. p. 359, pi. xviii. figs. 9, 10. 

 Retepora erassa, Busk, Zool. Chall. Exp., part xxx. p. 115, pi. xxvi. tig. 10; pi. xxvii. fig. 3. 



It would seem that the avicularia may be either oval or round, as in the Challenger 

 specimens examined. Stations 161 and 162, 33 and 38 fathoms, they are oval; while in 

 another specimen from Victoria they are usually round, and this is also the case in a 

 fragment from ofi" Green Point, New South Wales. There are usually two large pores 

 or pits on the front of the zooecium, near the proximal end. 



Habitat. — Victoria ; New South Wales. 



