316 THE INIABITANTS OF THE SEA. 
more information about the Brachiopods than an examinatio. 
of the finest collection of the living species. In each of the 
above excursions a different set of forms would be collected, for 
many of the palzeozoic genera have altogether disappeared when 
we rise among the secondary rocks, and in the latter we find 
forms which closely remind us of existing species, but which, 
though very near, are yet unquestionably distinct. In forma- 
tions of all epochs, a few generic types are common, and the 
' Lingule of the earliest sedimentary formations, presenting 
traces of organic life, strikingly remind us of the species of 
that curious group living in exotic seas at the present day.” 
At the lower extremity of the great series of molluscous 
animals we find the Polyzoa (Bryozoa, or Sea-Mosses) and 
Tunicata. The former, which comprise the Sea-Mats (Flustree, 
Escharz), the Sea-Scurfs (Lepralize), the Retepores, the Cellu- 
Jarize, and several other families, were formerly reckoned among 
the polyps, whom they greatly resemble in appearance and mode 
of life, but far surpass by the complexity of their internal or- 
ganisation. The Sea-Mats are among the commonest objects 
which the tide casts out upon our shores, for you will hardly ever 
walk upon the strand without finding their blanched skeletons 
among the relics of the retiring flood. 
Their flat leaf-like forms might easily 
% sl weeds, but a pocket-lens suffices to show 
Ml that they are built up of innumerable 
YiiG i! little oblong cells, placed back to back 
like those of a honey-comb, and each 
crowned by four stout spines, which give 
their surface a peculiarly harsh feel 
when the finger is passed over it from the apex to the base. 
“The individual cells,” says Mr. Gosse, “are shaped like a 
child’s cradle, and if you will please to suppose some twenty 
thousand cradles stuck side to side in one plane, and then 
turned over, and twenty thousand more stuck on to these bottom 
to bottom, you will have an idea of the framework of a flustra. 
And do not think the number outrageous, for it is but an ordi- 
nary average. I count in an area of half an inch square sixty 
cause them to be mistaken for dried sea- 
Leaf-hke Sea-Mat. 
