346 
cole: dry valleys in the chalk. 
less than 6,000 years. Such experiments must be mainly tentative, 
and the increased rainfall for the last few years shows that my 
estimate of 27 J inches of average rainfall was scarcely high enough. 
Still it may be confidently asserted that the result of the calculations 
is not far from the mark, and it may be inferred, that for every foot 
removed from the surface of the table-land, 2 ft at least are removed 
from the sides and bottoms of the valleys. 
NOTES ON CLASSIFICATIONS OF CYCLOSTOMATOUS POLYZOA: OLD AND NEW. 
BY GEORGE ROBERT VINE. 
From the time of Lamouroux and Goldfuss to the present, the 
group of organisms which we now characterise as Bryozoa, or 
Polyzoa, have received marked attention from naturalists. There 
has been, however, many misconceptions as to the true affinities of 
this, with other groups, — and many misunderstandings in con- 
sequence — but at the present time Polyzoa literature is becoming 
rather abundant, and the misconceptions are, to a large extent, things 
of the past. 
With regard to this preliminary paper, I may be allowed^to say 
that my object in writing it, is to place before the student the aims 
and outcome of the various classifications of the Cyclostomata 
extant, not for any desire of contesting the conclusions of the 
authors referred to, but more for the purpose of keeping controversal 
matter out of my future papers. 
The divisions of the Polyzoa now generally recognised by 
naturalists : — 
I. — Cheilostomata. 
II. — Cyclostomata ; and 
III. — Ctenostomata ; 
were originated by Mr. Busk in his catalogue''' of the Marine Polyzoa 
in the British Museum, and in the monogTaph of the Fossil Polyzoa 
of the Crag.f After the publication of the latter work, two elaborate 
papers followed from the pen of Professor Smitt, on Scandinavian 
♦ Parts I. and II. f 1859. 
