180 VINE: POLYZOA OF THE WEDLOCK SHALES. 
that is available for special detail, that is the cell; gi'owth and habit 
are less essential, but of relative importance, if the characteristic cell 
arrangement is well and carefully studied. In the following notes 
the whole idea of classification is built up from the knowledge of the 
structural arrangement of, or disposition of the cells, and the few 
characters associated with them. This will be more observable in a 
division of the Polyzoa which I have been compelled to found for the 
reception of certain species. There is one group of Polyzoa in the 
Silurian rocks, abundant both in this country and in America, the 
Stomatoporae, that seems to link the Silurian with the mesozoic and 
later epochs, though species of Stomatoporae are unknown, up to 
date, in the carboniferous series; while the Ascodictyae which are 
abundant in the Wenlock shales, and rare in the Scotch carboniferous 
shales, are present both in the Silurian and in the Devonian rocks of 
America. Species of this group may ultimately be regarded as the 
palaeozoic representatives of the stoloniferous Ctenostomata ; to some 
of the recent forms of this sub-order they bear a very close re- 
semblance. Of the Cheilostomatous group of polyzoa, so abundant 
and diversified in the present seas, I know of no forms by which, 
apparent palaeozoic types could be linked together, and it is very 
questionable whether the sub-order with all the varied characters now 
recognised by the systematist, had an earlier beginning than the 
middle jurrassic. Modified Cheilostomatous features may have ex- 
isted however in the Fenestelidae of the palaeozoic rocks. 
Secondly, there are throughout the whole of the palaeozoic rocks, 
both in this country and America, a very peculiar group of fossils, 
which are differently regarded, systematically, by different authors. 
One holding that the group belongs to the Bryozoa, another to the 
Coelenterata, I mean the Monticulipora, but as the w^hole system- 
atic question of generic or specific affinity has been ably discussed by 
Professor H. A. Nicholson in his admirable monographs, (Tabulate 
Corals, 1879 — and 'the genus Monticulipora, 1880.) I refer the 
students to these works for special details. At the same time it 
must be admitted that elaborate details on the American species, 
pointing in an opposite direction, are furnished by ^Ir. E. 0. Ulrich 
(Journal of the Cincin. Soc. Nat. Hist., 1882-1885) in his various 
