VINE : BRITISH PALEOZOIC CTEXOSTOMATOUS TOLYZOA. 93 
I have given illustrations of most of the varieties ; some have very 
few vesicles, in others the vesicles are more abundant. As the colonies 
are unevenly scattered over broken shells, stems of crinoids, &c, I 
have been obliged to draw the figures by the eye only, and not by the 
camera lucida, but the characters of all may be relied upon as being- 
true to nature. 
Plate IV. 
Fig. 1. Ascodictyon siluriense, Vine. 
This figure is drawn by the aid of the camera lucida from a 
transparent section of shell, on which the whorls were scattered, so 
that all the outlines are in proportion, and the fossil is magnified a 
little over twenty-five times. 
Figs. 2-2a. Valkeria tuberoso, Heller. 
This species is also drawn by the aid of the camera lucida, and 
it is magnified about the same, twenty-five times. This is a recent 
species, dredged by Dr. Pergens, in the Bay of Naples. It is placed 
here for the purpose of shewing the character of the Zoarium, the 
whorls of Zooecia, and the connecting hollow filamentous thread by 
which the whorls of cells are connected together. The striking simi- 
larity between the living and the fossil forms are at once apparent. 
Fig. 3 and 4. Ascodictyon Youngi, Vine. 
Fig. 3 is a magnified fragment of Crinoid stem, on which colonies 
of this species covered the whole of the surface. On account of the 
undulations of the stem it is impossible to depict the continuous 
ramifications of the filaments, hence they appear in the sketch as 
broken threads. Only one cluster of vesicles is shown, and these 
and the filaments are magnified to about the same proportions as 
figs. 1 and 2. 
Fig. 4. Two separated clusters of vesicles drawn by the aid of 
the camera lucida magnified to about 60 diameter. Examples in my 
own cabinet. 
