9 2 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Tremadoc rocks of North Wales." Mr. Homfray, of Portmadoc, than 

 whom no one has had greater experience or more carefully studied 

 the Tremadoc rocks in their original localities, finds no difficulty in 

 recognizing and correlating the rocks and fossils of the two districts, 

 affirming the St.-David's beds to be the equivalents of the lower 

 portion of the series in the Portmadoc region. Mr. Homfray is 

 also of opinion that the Upper Tremadoc rocks are represented at 

 St. David's by part of the Arenigs, which contain several Upper- 

 Tremadoc fossils, in addition to the rich fauna of Graptolites (42 

 species) now known to occur through the entire Arenig series. 

 The whole Tremadoc fauna consists of 33 genera and 86 species, 

 and no Hydrozoa ; the Arenig includes 62 genera and 149 species, 

 with 42 species of Hydrozoa ; the succeeding Llandeilo has 230 

 species, 90 of which are also Hydrozoa ; yet in each formation the 

 Graptolites appear mostly to be of distinct species. They also play 

 an important part in the faunas of the Llandeilo, Caradoc, and 

 Llandovery rocks of Scotland. 



Table VII. (p. ioo) is a complete numerical analysis of the 

 fossils in the Lower Cambrian rocks, from the Harlech and Long- 

 mynd to the close of the Upper Tremadoc, in which it will be seen 

 that the twelve classes (and Plantae?) are represented by 61 genera 

 and 182 species, as the known commencement of life in the British 

 area. They are as follows : — 



The Longmynd group contains 18 genera and 33 known species. 

 The Menevian „ „ 24 „ 51 „ „ 

 The Lower Lingula-flags „ 19 „ 38 „ „ 

 The Upper „ „ „ 12 „ 40 „ 

 The Lower Tremadoc ,, 26 „ 55 „ „ 

 The Upper „ „ 21 „ 34 „ 



11 genera and 16 species pass to the Arenig, this small number 

 clearly determining the individuality of the Lower Cambrian fauna. 

 It is only through the 6 species of Crustacea out of 103, and the 

 6 Brachiopoda out of 20, that the passage-forms are thus numerous. 

 The remaining 3 species are pelagic, 1 Pteropod, 1 Heteropod, and 

 1 Cephalopod. 



Lower Tremadoc. 



Plants. — None. Protozoa. — None known. 



Hydrozoa. — Dr. Callaway discovered in the Shineton Tremadoc 

 rocks two species previously unknown. One belongs to the genus 

 Clonograptus of Hall ; the other is the Bryograptus Callavei of 

 Lapworth, both belonging to the family Dichograptidse. These are 

 the oldest Ehabdophora known. 



Actinozoa. — None, so far as we know, below the Llandeilo rocks. 



Echlnodermata. — Dendrocrinus cambrenszs, Hicks, and Palceaste- 

 Tina ramseyensis, Hicks, are both from the Lower Tremadoc beds 

 of Eamsey Island, St. David's ; they are the first known species of 

 the orders Crinoidea and Asteroidea ; and they stand with numerous 

 other discoveries as a testimony of the value of the researches of 

 Dr. Hicks in these early Cambrian rocks, to which Paheozoic palae- 

 ontology owes so much. 



Annelida. — None, either in the rocks of South or North Wales. 



