Xil DESCRIPTIVE REMARKS. 
case the probability is, that the impressions left by such readily de- 
composing vegetable organisms would not have appeared so sharp and 
clearly defined as that of the Oldhamia presents in the fine sandstones, 
in which they occur so abundantly in certain situations. 
The remaining Fossils from the Irish Cambrians were discovered 
by Dr. Kinahan, who collected similar tracks and burrows to those de- 
scribed by Mr. Salter (Plate ii., fig. 3), as well as very large tubular 
burrows; some of which since obtained by the Geological Survey of Ire- 
land, passing vertically through the grit beds, are several inches in length, 
(fig. 4, ¢); this fossil Dr. Kinahan named Histioderma EHibernicum* 
(Plate ii., fig. 4); describing it as “‘a tentacled sea worm, evidently 
cephalo-branchiate, and not very dissimilar from the common Lugworm 
(Arenicola) of our present seas.’’ 
From this brief sketch of the Cambrian Fossils, it will be seen that in 
the great series of strata composing this, the oldest of the fossiliferous 
deposits in England and Wales, the earliest evidence of life indicates 
only the existence of marine animals referrible to Annelids, with a 
doubtful Crustacean. In Iveland similar tracks and burrows (Arenico- 
lites), with a larger and more evident form (/istvoderma), also Anneli- 
dan, occurs, and in addition the well-marked Sertularian-like Zoophytes 
( Oldhamia). 
Tt has been argued, and with reason, that this apparent paucity of 
organic remains may have arisen from the nature of the deposit ; arena- 
ceous or sandy beds being generally bad preservatives of organic 
structure; and that there may have been a more varied assemblage of 
life during this epoch, including marine plants, and some of the softer 
kinds of Zoophytes, Mollusca, or other invertebrate animals, of which 
no record remains, either from the perishable nature of their structures, 
or from their obliteration during the process of change, or consolidation 
of the deposit in which they were imbedded: as this, however, is ne- 
cessarily conjectural, much importance cannot be attached to it, 
We have not thought it necessary to allude more particularly to the 
Hozoén of the Laurentian Rocks of Canada, described by Sir William 
Logan and others, as the presence of that questionable Fossil has not 
been yet satisfactorily established in the British Islands. 
* Journ. Geol. Soc. of Dublin, vol. viii., p. 71. 
