THE CAMBRIAN PERIOD. Si 



beds of Lower Cambrian age at Bray Head, Wicklow, Ireland, 

 some very remarkable fosliils, which are well known under the 



, Fig. 28. Fragment of Eophyton Linneanum, a supposed land-p'ant, L 

 Cambrian, Sweden, of the natural size. 



name of Oldhamia, but the true nature of which is very doubtful. 

 The commonest form of Oldhamia (fig. 29) consists of a 

 thread-like stem or axis, from which spring at regular intervals 

 bundles of short filamentous branches in a fan-like manner. 

 In the locality where it occurs, the fronds of Oldhamia are very 

 abundant, and are spread over the surfaces of the strata in 

 tangled layers. That it is organic is certain, and that it is a 

 calcareous sea-weed is probable ; but it may possibly belong to 

 the sea-mosses (Polyzoa), or to the sea-firs (Sertularians). 



Amongst the lower forms of animal life (Protozoa), we find 

 the Sponges represented by the curious bodies, composed of 

 netted fibres, to which the name of Protospongia has been given 

 (fig. 32, a); and the comparatively gigantic, conical, or cylin- 



