Notes on Graptolites and allied Fossils occurring in Ireland

Abstract

T he remarks I am about to offer upon a group of fossils of great importance in determining strata of Silurian age is principally intended to record the species I have been enabled to identify in Irish strata. I shall avoid discussing the question as to the exact position Graptolites occupy in the animal kingdom, except to observe that the preponderance of evidence is in favour of their alliance with the Hydrozoa; nor will I give any details of their structure, this subject having been lately so ably discussed by Mr. William Carruthers in the new edition of ‘Siluria,’ and in his paper entitled “A revision of the British Graptolites”* Dr. H. A. Nicholson has also added considerably to our knowledge of this interesting group of extinct Zoophytic organisms. I will now briefly allude to the localities in Ireland where these fossils occur, nearly all of them having been visited by me, and numerous specimens examined in connexion with my duties on the Geological Survey of that country. Commencing with the south of Ireland, the first place to be noticed is in the county of Waterford, on the banks of a stream called the Dalligan river, five miles N.E. of Dungarvan, where dark grey argillaceous shales occur full of the small diverging Graptolite, Didymograpsus sextans , Hall; they were first discovered at this place by Mr. Charles Galvan, of the Geological Survey. In the list of fossils, appendix to ‘Siluria,’ 1867, the geological range of this species is limited to the Llandeilo