416 MISS E. M. E. WOOD 01* THE LOWER LUDLOW [May 1900, 



fauna at a corresponding horizon in Europe have long been 

 known from the discoveries of Continental geologists. But little or 

 nothing has hitherto been worked out with respect to the vertical 

 range of the individual graptolite-species within the limits of the 

 formation itself, or with regard to their geographical distribution 

 in the equivalent strata of Wales and the West of England. 



During the last few years I have devoted much of my leisure-time to 

 the study of the graptolitic fauna, the rock-sequence, and the vertical 

 distribution of the various graptolite-species in the recognizable 

 subdivisions of the Lower Ludlow Shales of the typical Ludlow 

 district and of their equivalents along the Welsh Border, in order 

 to ascertain (1) what are the truly characteristic graptolites of 

 Lower Ludlow age as distinct from those of the Wenlock formation, 

 and (2) to what extent the Lower Ludlow Beds are capable of 

 subdivision into graptolite-zones. My results and conclusions are 

 embodied in the present paper. 



It is now generally acknowledged that graptolites are among 

 the most reliable fossils for purposes of correlation in the Lower 

 Palaeozoic rocks. And the graptolite-fauna of the Lower Ludlow 

 Shales is of more than ordinary interest, for it is the last distinct 

 assemblage of these fossils presented to us before the extinction 

 of the group. Notwithstanding the interest of this particular 

 assemblage of graptolites, it has hitherto received but little 

 attention in Britain. The reason for this neglect is evident. Most 

 of the species of graptolites hitherto recorded from the British 

 Lower Ludlow Beds belonged to forms originally described by 

 Barrande in his famous work on the 'Graptolites de Boheme,' 

 as early as the year 1850 ; but in some cases he included more 

 than one species under a single specific name, and consequently 

 correct identifications of the British forms were impossible until a 

 thorough revision of Barrande's Bohemian type-specimens had been 

 made. This revision has now been carried out by Dr. Jaroslav 

 Perner (' Etudes sur les Graptolites de Boheme ' pt. iii), and 

 through his kindness I have also been enabled to examine Bar- 

 rande's type-specimens for myself on the occasion of a recent visit 

 to Bohemia. 



Much of the present paper is necessarily palseontological, and 

 consists of descriptions and figures of the more important species 

 of Lower Ludlow graptolites. I have endeavoured to limit the 

 number of species and varieties as much as possible, and have 

 restricted myself mainly to the description of such forms as are of 

 greatest value for stratigraphical purposes. 



In working out the stratigraphy of the Lower Ludlow I have 

 studied three districts in some detail, namely : — 



(1) The Ludlow District, where the defining limits of the formation are 



well marked by calcareous beds of considerable thickness ; 



(2) The Builth District, where the calcareous limiting-beds are still faintly 



indicated, but the lithological boundaries are more or less indefinite ; 



(3) The Long Mountain District, where the calcareous limits are absent, 



and no definite lithological boundaries exist. 



