448 Br. J. W. Sjjencer — The Antillean Continent. 



and the overlying Arenig rocks was then mainly adopted owing 

 to the discovery by us of very rich Graptolite zones in the overlying 

 slates, and to the recognition by Mr. J. Hopkinson of over 20 species 

 belonging to genera characteristic of the Quebec Grroup of Canada.^ 



In the Quart. Journ. Geol. Soc. for 1880, p. 237, there is an 

 important communication from Prof. T. McKenny Hughes, in which 

 it is stated that beds in Anglesey which had hitherto been " referred 

 to the Garadoc are Tremadoc ; that they are succeeded by Arenig." 

 In these beds he found Orthis Carausii, and Neseuretus Ramseyensis, 

 a characteristic Tremadoc form, and he states that " they exactly 

 resemble specimens from the Tremadoc of Ramsey Island (St. 

 David's) in the character of the rock and mode of preservation 

 of the fossils." 



Although I have had to limit my summary to that portion of the 

 Lower Palaeozoic I'ocks now usually classified under the name 

 Cambrian, I think it must be granted that the researches carried 

 on in these rocks during the past thirty years have been most 

 fruitful in important results. During this period the doctrine of 

 evolution has exerted a powerful influence on geological thought ; 

 and no one who can call to mind the state of our knowledge before 

 that time can possibly deny that the influence has been for good. 

 Of necessity, those who were working on the earliest known faunas 

 kept this doctrine continually in view, and I believe there are few 

 at the present time who will not admit that evidence in its favour 

 has constantly increased in strength as the gaps in the succession 

 were being filled up. 



III. — Eestoration of the Antillean Continent.^ 

 By J. ^Y. Spencer, Ph.D., M.A., B.A.Sc, F.G.S. 



THERE have been many suggestions respecting a continental 

 connection of the West Indies, but this is the first attempt 

 made to restore the Antillean lands. It is based upon the slowly 



1 These, with many additional forms obtained by us from the Arenig rocks of St. 

 David's, were afterwards described by Messrs. Hopkinson and Lapworth in the 

 Quart. Journ. Geol. Soc. vol. xxxi. p. 632 (1875), and in the discussion of that 

 paper Mr. Hopkinson said "that the dendroid forms are only known to occur in 

 abundance in Britain in the Arenig rocks of St. David's, and that there are 

 intermediate forms connecting British and American .species which occur in rocks 

 of more ancient date." He further remarked that he "did not consider the 

 dendroid forms vahiable for determining zones, species very nearly allied to those of 

 the Arenig rocks being met with even in the Lower Ludlow rocks of Shropshire ; 

 but the Ehabdophora occur only in small zones, and wherever they are found they 

 seem to hold an equivalent position. They are consequently valuable for strati- 

 graphical purposes." In the same paper they give a Table "in which every species 

 (obtained in the vicinity of St. David's) is referred to its exact position in the 

 vertical series," and in page 639 they say: "Perhaps the most patent result of 

 these researches is the circumstance that they clearly demonstrate that the Hydroida 

 of these ancient rocks, so long shunned or misinterpreted by the systematist, are 

 rapidly emerging from the obscurity which has enveloped them, and will perhaps 

 soon stand side by side with the better understood Brachiopoda and Crustacea, as 

 unerring exponents of the true geological age of the most widely separated rocks 

 in which they are found." 



2 Abstract of a paper read before the Geol. Soc. of America, August 14th, 1894. 



