TRANSACTIONS OF THE SECTIONS. 



5$ 



of the Secondary System, including under that term all deposits from the Triassic to 

 the Cretaceous. They are characterized by Graptolites and many peculiar genera of 

 Corals, by a vast abundance of Brachiopods, by Trilobites, and by peculiar forms of 

 Cephalopods. On the other hand, a few species are continued through a great as- 

 cending series of groups, from the Cambrian to the Carboniferous ; and between the 

 successive primary or palaeozoic groups, it is very diflScult, and sometimes (in the 

 actual state of our information) impossible to draw a well-defined line of separation. 

 Hence (although all the types of organic life, from the oldest palaeozoic to the modern, 

 belong properly to one Systema Natures) it is convenient for description to regard 

 the palaeozoic fauna as a sufficiently distinct Systema Naturce to have a separate 

 aame as a system. 



In vindication of the previous statements the author quotes the following exam- 

 ples of fossils which have a wide palaeozoic range : — 



Favosites alveolaris, from the Bala group to the Devonian inclusive. 



gothlandica „ „ „ Carboniferous „ 



Hexopora fibrosa „ „ „ Devonian „ 



Spirigerina reticularis „ „ „ Devonian „ 



Leptagonia depressa „ „ „ Carboniferous „ 



and he doubts not that several other species might be added to the list. 



After these preliminary remarks the author gave the following Tabular Views. 



Upper 

 division. 



Middle 

 division. 



[ill. 



iBt. Tabular View of the British Palxozoic System. 



Permian series. Divisible into three subordinate groups. 

 Carboniferous series. Divisible into three or four subordinate groups. 



Devonian 

 series. 



Lower 

 division. 



5. Ludlow group. 



4. Wenlock group. 



3. Bala group or 



Upper 



Cambrian. 



2. Festiniog group. 



1. Bangor group. 



' 8. Petherwin group. 



7. Caithness group? [perhaps, capable of further subdivision. 

 6. Plymouth group, without any ascertained base, and therefore, 

 ~ d. TUestone. 



c. Upper Ludlow. 



b. Aymestry limestone. 

 II. Silurian J L a. Lower Ludlow. 



d. Wenlock limestone. 



c. Wenlock shale. 

 b. Woolhope Umestone. [Umestone. 



a. May Hill sandstone and Pentamerus 



b. Upper Bala — Caradoc sandstone and 

 shale; Hirnant and Bala limestones; 

 flagstone and conglomerate, &c. &c. 



a. Lower Bala — dark slates, flags, grits,&c. 

 I. Cambrian f ^ Arenig slate and porphyry. 



b. Tremadoc slate. 



a. Lingula flags. 



c. Harlech grits. 



b. Llanberris slates*. 

 a. Longmynd slates. 



This tabular view (chiefly derived from the Welsh sections) agrees very nearly with 

 one published by the author in the 2nd Fasciculus of the Palaeozoic fossils in the 

 Cambridge Museum, two changes only having been introduced : 1st, the Longmynd 

 slates are arranged provisionally with the lowest or Bangor group ; for they form 

 the oldest group (not metamorphic) in the Cambrian and Silurian country, and by 

 the gentlemen of the Government Survey they are regarded as the base of what is 

 here called the Bangor group. 2ndly. The May Hill sandstone and Pentamerus 

 limestone are now cut off from the Caradoc sandstone, and placed at the base of the 

 Wenlock group. Some of the reasons for this latter change were given in a paper 

 read before the Geological Society of London, Nov. 3, 1852, and are now published 

 in No. 35 of the Journal of the Geological Society of London (Aug. 1853). 



The previous tabular view is derived from the sections of Siluria and Cambria. 



* This sub-group (Llanberris slates) is of great thickness, and includes several bands of 

 slates and hard grits which are below the great quarries of Nant Francon and Llanbeiiis. 

 These quarries are immediately under the so-called Harlech grits. . 



