200 
Mr. A. W. Waters on the 
more solid than in R. Couchii ; the lower lip is not raised, 
but has a small rounded avicularium in the aperture. In 
this respect it agrees with fig. 7, pi. xii., in Busk’s ‘ Crag 
Polyzoa,’ which he calls R. Reaniana , King; but, from the 
descriptions, I cannot veuture on giving synonyms. Scat¬ 
tered over the cells are minute round avicularia; and the same 
are fairly numerous on the dorsal surface. Both on the back 
and the front there are pores about the same size as the 
avicularia, differing only in having no cover; and the same 
thing occurs in the African Eschara contorta, where some of 
the pores have avicularian covers and some are open. In 
considering the function of the avicularia the small ones 
should receive as much consideration as the large sessile ones, 
which are more easily studied; and in these cases there seems 
a strong indication of the function being somewhat the same 
as that of the tube-pores, which are filled with the chylaqueous 
fluid. It is also an important fact that in the Cheilostomata 
the zooecia have covers (opercula), and also the avicularia 
(mandibles), while in the Cyclostomata the zooecia are open 
and the u adventitious tubules ” are also without a cover. 
Opercula somewhat saddle-shaped; distal edge rounded, 
proximal nearly straight; long muscular bosses at the side, 
0‘09 millim. wide, 0‘084 long. 
Loc. This occurs in the Crag, and generally in the Pliocene 
of Italy and Sicily ; but, from the descriptions from other loca¬ 
lities, it must remain uncertain whether this is the species 
described. Living: Arctic Seas, Mediterranean, Australia. 
76. Retepora Couchii , llincks. 
(PI. XV. figs. 3, 4, 5, 6.) 
Retepora Couchii , llincks, On the genus Retepora, Ann. & Mag. Nat. 
Hist. ser. 5, vol. i. p. 355, pi. xviii. tigs. 1-6. 
Retepora Reaniana, Hincks, Ann. & Mag. Nat. Hist. ser. 3, vol. ix. p. 
306. 
Retepora cellulose, Manzoni, Bry. Foss. Ital. cont. 4, p. 19, pi. v. 
figs. 26, 28. 
This is a most beautiful delicate form, which is not so 
abundant as the last. In some cases the raised avicularia are 
wanting, when we have Manzoni’s cellulosa (fig. 28); and 
this is certainly the cellulosa of many authors. The young 
cells (fig. 5) have six spines; but, except in the youngest 
colonies, I have not found any spines. The round avicularia 
are larger than in the last species; and, besides these, there 
are long acute avicularia covering the lower part of a zocecium, 
and on the dorsal surface there are similarly rounded and 
large acute avicularia ; betweer* the zooecia is a slightly raised 
