556 REPORT—1885. 
Primary orifice sub-orbicular or semicircular; border entire. Afterwards 
the peristome becomes much raised and multiform, usually fissured in the 
middle or one side in front, the fissure often becoming a sub-oral pore by 
the meeting of the upper angles. Very often a small avicularium on one 
of the angles, which is also frequently developed into a labial or pre-oral 
rostrum. Usually numerous adventitious avicularia on one or both 
aspects of the zoarium.’—Ohal. Rep., pp. 105, 106. 
I suppose that there are not among the whole of the recent Polyzoa 
two more difficult groups to master the details of than the Retepore and 
the Cellepore. I know too well that this is painfully true of the fossil 
species that have been placed in either of these respective groups. My 
early dissent from the supposed identity of the Paleozoic forms with 
recent species was very early expressed in my crude articles in ‘Science 
Gossip,’ and later on in the earlier of my ‘ British Association Reports’ 
(Carboniferous, 1880, and Silurian, 1881) ; andit must be remembered that 
at this time very little attention had been paid to the inner structure of 
either fossil or recent forms, so that even up to a very recent date 
Paleozoic species, which were fenestrated by the inosculation of branches, 
were indifferently placed among the Reteporide as then understood. — 
Within the last six or seven years a very great advance has been made in ~ 
the study of parts of the zoarium of fossil species of Polyzoa; and the 
remark is especially applicable to the study of parts of the zoarium in 
recent forms of several groups of Polyzoa. One of the comparatively 
recent additions to our knowledge of parts of the zoaria of species is that 
of the Rossenplatten (communicative pores of Hincks), through which the — 
endosarcal cords passed from cell to cell. This, though eminently avail- 
able for the classification of recent species, is not so available for the more — 
minute study of fossil species. Another more recent addition to our 
knowledge of the chitinous appendages of species was made by Mr. A. W. 
Waters in a communication to the Geological Section of the Manchester 
Literary and Philosophical Society, and ultimately published in their ‘ Pro- 
ceedings’ (vol. xviii. No. 2, Sess. 1878-9). The paper referred to was 
one on ‘ The Use of the Opercula in the Determination of the cheilosto- 
matous Bryozoa.’ Mr. Waters figures and describes thirty-seven species — 
of opercule, all magnified eighty-five times, and his specimens were 
selected from a much larger group of forms than those enumerated. This 
paper seems to have been entirely unknown to Mr. Busk until after the~ 
drawing up of the Descriptive Catalogue of the Species of Cellepora 
collected in the ‘Challenger’ Expedition (‘ Linn. Soc. Journ. Zoology,’ 
vol. xv. 18817). In a ‘supplementary note respecting the use to be 
made of the chitinous organs in the Cheilostomata, &c.’ (‘ Linn. Soe. 
Jour.’ vol. xv.), Mr. Busk speaks his regret, acknowledges the value of 
the paper by Mr. Waters, and then says (loc. cit. p. 357): ‘ But having 
since devoted much attention to this point, and examined the characters 
not only of the operculum, as suggested by Mr. Waters, but also, in 
addition, those of the other chitinous elements of the skeleton in between — 
sixty and seventy species of Cellepore, as well as in numerous species of 
Retepore and Salicornariade, both groups in which the determination of 
species is often attended with considerable difficulty and uncertainty, 1 
have become convinced that the characters derived from the chitinous 
organs will be found of the greatest possible utility, and at the same time 
capable of being employed with the utmost facility and precision.’ The 
new knowledge derived from the study of the chitinous parts of recent 
ia 
