29 
Bryozoa of the Bay of Naples. 
in the 1 Denkschriften ’ of the Vienna Academy, have been con¬ 
stantly consulted, as also the completion of the work by Dr. 
A. Manzoni, who has so ably taken up the study of the Italian 
Pliocene Bryozoa, and has published a series of papers in the 
‘ Sitzungsberichte’ of the same Academy, together with one on 
a few forms of recent Bryozoa. Smitt’s papers and Busk’s 
catalogue are the text-books employed. 
For convenience I commence this paper with Lepraloid forms 
—though, as I am quite convinced that the genus Lepralia , 
as now understood, must soon be abolished, the division may 
seem very strange; but classification is in the first place useful 
for mere arrangement and for enabling zoologists to know with 
certainty what is meant when any species is mentioned, and 
the classification of the British-Museum Catalogue has assisted 
in this direction; but as knowledge advances an artificial ar¬ 
rangement has to give way before that which is more natural. 
Smitt, the most careful observer of these animals, has pro¬ 
posed a classification in which the greatest weight is given to 
the form of the zooecia, and the shape of the aperture is largely 
used, instead of making the colonial form of growth the most 
important. Our own countryman, Dr. Hincks, has quite re¬ 
cently proposed, in these pages, a classification in much the 
same direction as Prof. Smitt; and both of these are, in my 
opinion, much superior to that in more general use. My 
reason for not at present adopting either is that there seem so 
many points which have not yet received their due attention, 
and there is so much material not yet worked up, that, for my 
own part, I am inclined to wait a short time, lest further 
knowledge should show that change is again necessary. The 
researches of Barrois on the embryology may furnish some 
landmarks. I have also noticed that the form of the oper¬ 
culum * is a most useful character in determination, as, besides 
showing difference in size and shape, the hinge of many is 
characteristic ; and the position of the opercular muscles is 
another guide. In some cases the muscles are at the edge of 
the operculum ; in others they are attached nearer the middle. 
A disk in the diaphragm of the Ctenostomata, and on the sides 
of the Cheilostomata, has been noticed by Reichert, Smitt, 
Nitsche, Ehlers, and Joliet, and has been called bythemthe “Ro- 
* “The Use of the Opercula in the Determination of the Cheilo- 
stomatous Bryozoa,” Proc. Manch. Lit. & Phil. Soc. vol. xviii. 1878. 
In the present paper I will refer to the figures in the communication 
just cited by giving the number of the figure after the word operculum 
—thus, operculum (1*) means fig. 1. 
For comparison the opercula should be examined by a power magni¬ 
fying about 250 times. 
It is scarcely necessary to say the principal value of the measurements 
is in giving the proportion of length to width. 
