HORNE: PREHISTORIC REMAINS DISCOVERED IN WENSLEYDALE. 179 
often within their enclosure. The housesteads occupied am iddle 
position between the river and the top of the hill. The people who 
occupied these housesteads are later than those that lived on the 
camping ground and in the cave, as we find in the latter no bronze 
or iron, while in the housesteads referred to both bronze and iron 
have been found. 
NOTES ON THR POLYZOA OF THE WENLOCK SHALES, ETC. 
BY GEORGE ROBERT VINE. 
PART I. 
Polyzoa (or bryozoa) from the upper and lower Silurian horizons 
of America have been described by Mr. James Hall and Professor 
H. A. Nicholson, and the bryozoa of the Cincinnata and Minnesota 
group of rocks have been systematically worked out by Mr. E. 0. Ulrich. 
But even now we are unable to correlate, satisfactorily, palaeozoic with 
the earlier mesozoic, much less with cretacious or tertiary forms. 
First, the most characteristic of the palaeozoic polyzoa have peculiar 
facies. In the Silurian rocks we meet for the first time with fenestrated 
forms with two individualised characters, one with branches united by 
disseppiments, and another by inosculation. Both these types are 
persistent throughout the whole of the palaeozoic series, whether in 
this or in other countries, while an equally persistent pinnated type 
begins low down in the series, and increases numerically and speci- 
fically till they reach the apex in the carboniferous rocks, both groups 
gTadually fading away in the Permian, and are entirely unknown in the 
mesozoic epochs. The peculiar Ptilodictya group begins in the earlier 
Silurians, and fades away before the close of the Devonian period, 
while another form, the Cystodictya, dies out entirely in the carboni- 
ferous limestone series of rocks. All the species of these various 
genera are well marked and distinct, and rocks may be characterised 
whenever individual specimens are present. In describing any one 
of the species of these groups there is only one element of structure 
