A. W. WATERS—REPORT ON THE BRYOZOA. 139 
threads which often form quite thick cords, seen, however, to be formed of 
finer threads. Granular masses, which stain, are sometimes included in these 
cords. 
There are 15 tentacles, and I have seen no intertentacular organs. 
Loc. Florida ; Victoria ; Queensland ; Ceylon ; Indian Ocean ; Zanzibar ; 
Khor Shinab (3), Khor Dongola, 9} fath. (4), Suakim, 5 fath. (7, 8), Suez 
Docks (20), collected by Crossland ; lat. 16° N., long. 41° W., 30 fath., and 
Gimsah Bay, collected by Loffler & Siemens. It is also found fossil in the 
Crag and the Tertiaries of Europe, Australia, and Egypt, and probably some 
Cretaceous fossils known under other names should be placed here, but the 
discussion of the fossils is postponed to a future occasion. 
MermMBRANIPORA ? BURSARIA (MacGillivray). (Plate 12. fig. 10.) 
Amphiblestium bursarium, MacG. Trans. R. Soc. Vict. vol. xi. (1886) p. (3), pl. 2. fig. 2. 
Siphonoporella bursaria, Thornely, ‘ Manaar,” p. 111. 
Miss Thornely is right in placing this with the Siphonoporella of Hincks, 
though it is doubtful whether the genus can be retained. I have a specimen 
from West Australia sent to me as Stphonoporella nodosa, Hincks, and which 
I believed to be the co-type, though it does not correspond entirely with 
Hincks’s figure and description, as it has a tubercle at each top corner of the 
zocecium and it has a vicarious avicularium, broader and shorter than the 
one figured on my WM. bursaria, var. phillipensis*. Hincks wrote “no 
avicularia,” and in no specimens that I have seen are they frequent, being 
only found here and there. Hincks does not seem to have correctly appre- 
ciated what he called a siphon, for it is a tube + or neck through which the 
polypide is extended from the broader part of the zocecium to the surface ; 
and in this group, instead of being central as in Micropora, Steganoporelia, 
Thalamoporella, it is frequently entirely to one side, with a large hollow 
space on the other side. In Mlicropora, as shown by Jullien, these two 
hollow spaces, or opesiules, contain the muscles, which pass from the base up 
to the membrane covering the zocecium, thus drawing the membrane down 
and acting as a compensation sac. Now in Stphonoporella nodosa, H., 
although usually lateral, we sometimes see a hollow on each side ; while, on 
the other hand, some specimens of M. bursaria, from Victoria, only occa- 
sionally show the lateral position, so that it may be readily overlooked. 
The Red Sea specimen, although in spirit, must have been long dead when 
collected, and I have been unsuccessful in obtaining any material for studying 
the opesial muscles ; however, the operculum is Membraniporidan, and we 
seem here to be able to follow the changes from such a form as JZ. Rosselii 
up to irregular Siphonoporella of Hincks. Sitphonoporella and Thairopora 
* Journ. Linn. Soc., Zool. vol. xxvi. (1898) p. 690, pl. 49. fig. 11. 
t+ See Waters, ‘On Australian Bry.,” Ann. Mag. Nat. Hist. ser. 5, vol. xx. p. 186 & fig. a. 
LINN. JOURN.—ZOOLOGY, VOL. XXXI. 1a! 
