396 Baily— Cambrian Rocks and Fossils. 
sometimes as a dense and matted mass, which appears to permeate 
the rock in every direction where fractured, and to spread over the 
surface of the numerous beds in successive layers. The beds which 
contain it are sometimes several feet thick, and generally harder 
and more compact than those in which O. antiqua are found; they 
occur in either purple or green grits, most frequently perhaps in 
the latter, and on separating the laminz the fossils are seen to 
be slightly in relief on one surface, whilst the opposite bears a cor- 
responding indentation. 
Some difference of opinion has been expressed, more particularly 
by men of science in other countries, as to whether these fossils 
should properly be referred to the animal or vegetable kingdom ; 
some Continental writers having figured and described then as 
fossil plants—others again have even doubted their being organic at 
all, considering them merely to be markings caused by a peculiar 
mechanical condition of the rock. By the majority of Palzontolo- 
gists in this country, their zoological affinity appears to be accepted, 
in accordance with the eminent men who have published their views 
as to the animal origin of these fossils; and, considering them in the 
same light, their alliance with the Sertularian Zoophytes—which they 
resemble so closely—as first suggested by the late Professor Edward 
Forbes, appears to be the most reasonable conclusion as to their re- 
lationship we can arrive at. On the other hand, their resemblance to 
certain jointed marine plants, such as the lime-secreting Nullipores, 
would incline us to hesitate befure pronouncing with certainty as to 
their animal origin. As to their being organic, and not a mere mineral 
condition of the rock, there can, I think, be no question, because we 
find the representatives of each species, although often varying in 
shape and size, presenting the same general definite characters, not- 
withstanding their being isolated from each other; and although 
sometimes appearing to form an homogeneous mass permeating the 
rock, yet the surfaces of the beds show them to be deposited in hori- 
zontal layers between those surfaces, consisting occasionally of a 
few scattered examples, at other times of a more or less matted 
assemblage. 
The articulated character of the branchlets, which was considered 
by Professor Forbes to indicate the position of minute cells, and the 
presumed discovery by Dr. Kinahan of ‘reproductive cells,’ do not 
appear to me to be satisfactorily established, as, after an examination 
of the original and a number of other specimens, the only conclusion 
I can arrive at being that the jointed appearance they often exhibit 
is analogous to the structure presented by the NVullipores, or lime- 
secreting plants, before alluded to. 
That there is a general similarity of Oldhamia antiqua to certain 
recent Hydroid Polypes (popularly known as Corallines), such as the 
arborescent forms of Sertularia cupressina and argentea,* is very evi- 
* For excellent figures and descriptions of both these varieties, see Johnston’s 
‘British Zoophytes,’ pl. 15 and 16, vol. ii. pp. 79, 80; vol. i. pl. 14, fig. 3, and 
15 and 16, vol. ii. ! 
