ANNIVERSARY ADDRESS OF THE PRESIDENT. 



171 



tomata and Phyllopoda in the Ludlow rocks (45 species), which 

 stand alone as a peculiar and local group ; their presence there- 

 fore need not enter into the calculation *. The great extension of 

 the Weulock promontory to Welliugtou, running parallel to the 

 Dudley beds, and the overlap and cover of the Triassic rocks to the 

 north on to the Mersey, Liverpool Bay, Lancaster and Morecambe 

 Bays, go far to lead us to believe that the missing evidence of 

 the agreement between the Ludlow of the two areas of Wales and 

 Westmoreland, as well as the unsatisfactory correlation of the Den- 

 bighshire Grits and Tarannon Shales with the rocks of the Lake 

 country, can be accounted for ; for it must be admitted that much has 

 yet to be done with these Lower Wenlock rocks of Denbighshire, 

 Westmoreland, &c. The Kendal group (or the Ludlow rocks) and 

 the Ireleth Slates, which are the equivalents of the Wenlock of the 

 south, can certainly be correlated palaBontologically, dissimilar as they 

 appear physically. The Scotch uppermost Silurians are exhibited 

 only in three localities ; to the south of Kirkcudbright and in the 

 Pentland Hills both the Wenlock and Ludlow groups occur. The 

 American series termed the Lower Helderberg group are the true 

 equivalents of our Lower and Upper Ludlow, and contain a number 

 of species in common. The exact equivalent of the Oriskany Sand- 

 stones may be our lowest Devonian. In North America their place 

 is either at the top of the Upper Ludlow or between that and the 

 lowest Devonian rocks, or " Corniferous beds" of the American 

 geologists. I now attempt to analyze the extensive fauna of the 

 Ludlow group, accepting the triple division unconditionally ; or, in 

 other words, retaining the Aymestry Limestone as a distinct subfor- 

 mation, not attached either to the Lower or the Upper Ludlow ; its 

 accidental position carries with it certain fossils having an important 

 bearing upon physical geology. 



Plantje. — For the first time above the Wenlock we meet with what 

 may be termed plants proper ; yet the two genera Chondrites and 

 Fucoides are doubtful. 5 genera and 5 species are known ; 4 

 species occur in the Upper Ludlow, and 3 of the same in the 

 passage-beds between the Upper Ludlow and Lower Old Red Sand- 

 stone ; none are known in the Lower Ludlow or the Aymestry beds ; 

 nowhere in the Ludlow of either South or North Wales, Westmore- 

 land, or Ireland are plant-remains known. Actinophyllum plicatum 

 occurs in Shropshire and Herefordshire ; Chondrites verisimilis is an 

 Upper Ludlow form in Scotland. The seed-like bodies of doubtful 

 affinities (Pachytheca sphcerica) occur in the tilestones and bone-bed 

 of the uppermost Ludlow of Shropshire, Worcestershire, and Here- 

 fordshire. Actinophyllum and Pachytheca here first occur, and do 

 not pass to the higher formations. The passage-beds contain Acti- 

 nophyllum plicatum, Chondrites verisimilis, Pachytheca sphoerica, 

 and Pachy sporangium pilida. 15 species of Crustacea, 19 species 

 of Lamellibranchiata, 6 species of Gasteropoda, 4 species of Hetero- 

 poda, and 6 species of Pish, or nearly 70 species, illustrate 10 classes 



* Phyllopoda (Ceratiocaris 14 species), Merostomata (Eurypterus 10 species, 

 Hemiaspis 6, Pterygotus 9, Slimonia 3, and Stylonurus 3). 



