82 HISTORICAL PALEONTOLOGY. 



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- 

 drical fossils termed Arch&ocyathus by Mr. Billings are certainly 

 referable either to the Foraminifera or to the Sponges. The 

 almost total absence of lime- 

 stones in the formation may 

 be regarded as a sufficient ex- 

 planation of the fact that the 

 Foraminifera are not more 

 largely and unequivocally rep- 

 resented; though the exist- 

 ence of greensands in the 

 Cambrian beds of Wisconsin 

 and Tennessee may be taken 

 as an indication that this class 

 of animals was by no means 

 wholly wanting. The same 

 fact may explain the total ab- 

 sence of corals, so far as at 

 present known. 



The group of the Eichi- 



nodermata (Sea-lilies, Sea- . F1 - 29 .-A portion of oidhamia an- 



tiqua, Lower Cambrian, Wicklow, ire- 

 urchms, and their allies) is land, of the natural size. (After Salter.) 



represented by a few forms, 



which are principally of interest as being the earliest-known 

 examples of the class. It is also worthy of note that these 

 precursors of a group which subsequently attains such geo- 

 logical .importance, are referable to no less than three distinct 

 orders the Crinoids or Sea-lilies, represented by a species of 

 Dendrocrinus; the Cystideans by Protocystites; and the Star- 

 fishes by Palasterina and some other forms. Only the last 

 of these groups, however, appears to occur in the Lower 

 Cambrian. 



The Ringed-worms (Annelida), if rightly credited with all 

 the remains usually referred to them, appear to have swarmed 

 in the Cambrian seas. Being soft-bodied, we do not find the 



