392 
VINE: NOTES ON FOSSIL POLYZOA. 
common ancestral origin, but it is difficult to say where species 
originated. 
One of the differences between certain of the American and the 
Yorkshire forms may be noted. In some specimens of S. Nicklisi, 
Ul., from Kaskaskia, there appears to be delicate ridges developed 
in parallel or wavy lines, which seems to separate the cells into 
parallel or waving rows ; in other specimens, especially in the 
younger portions of the branch, that is in the apices, there are no 
ridges, and in this respect both the A.merican and British forms agree. 
The possession of other fragments from the British rocks would 
reveal perhaps the separating ridges also, but my own Yorkshire 
specimen is the younger or growing part of the branch. 
The specimen described is about 1^ line in length, and about \ 
line in width. In the whole length of the fragment taking a row 
of cells, I find there are about 7 cells, or being more accurate, 6J 
cells. A fragment of the American form of the same dimensions, 
for some specimens are more bulky than ours, affords the same 
results. 
Localities : Hurst, Yorkshire ; Kaskaskia, 111. ; Chester group. 
Reference to PI. XXI. 
Fig. 1 , Heterotrypa delicatula, Vine, natural size and magnified. 
Fig. 2, Diplotrypa sp., var. petropolilanaforma. Vine, „ 
Fig. 3 ? Ceramopora megastoma. Yorkshire specimen. 
Fig. 4, Streblotrypa Nicklisi, Ulrich. Yorkshire form. 
Fig. 5, ,, „ „ American form. 
Only in some cases there are three rows of punctures below the 
cells mouth. 
The present paper completes my record of researches on York- 
shire Monticuliporidse and Polyzoa, unless other material be forth- 
coming. It is a great pity that our younger naturalists can find so 
little to interest them in Yorkshire material. In writing to me in 
acknowledgement of the receipt of my paper on North Yorkshire 
Eydomostraca, Mr. J. W. Kirkby remarked, " You will probably find 
many more species of Entomostraca in the Garb. Rocks of Yorkshire, 
if you continue your researches, especially in the calcareous shales 
