Distribution of the Rhabdophora. 369 



sional recognition of a fragmentary specimen of Rhabdophora 

 in these deposits incapable of specific identification, nothing is 

 known of their further existence. 



In the great mudstone series of the Salopian of Siluria, 

 at least two fairly distinct zones are at present recognizable. 

 The base of the Wenlock from Llangadock to Bala and Grlyn 

 Ceriog, as well as in the Lake district itself, is formed by a 

 series of dark shales and flags marked by the presence of 

 Cyrtograptus Murchisoni, Carr. It is accompanied by the 

 other forms enumerated under this head in the accompanying 

 Table, some being survivals from the Tarannon fauna, and 

 others strictly peculiar to the Wenlock shales. The same zone 

 is recognizable in Scania, occupying a similar stratigraphical 

 place and yielding a corresponding Graptolite fauna. 



In the main mass of the Wenlock shales Cyrtograptus 

 Linnarssom, Lapw., is the most conspicuous form near 

 Builth. Of the fossils peculiar to higher horizons we as yet 

 know little ; but it may be expected that we shall in the 

 future meet here with the zone of M. testis, Barrande, which 

 has hitherto remained undiscovered in Britain, but has a wide 

 geographical range on the European continent. 



The most abundant forms of Wenlock age in Britain are : — 

 M. vomerinus, Nich., which is ubiquitous in its distribution ; 

 M. rtccartonensis, a most prolific Scotch species ; and M. 

 jjriodon, Bronn, which does not appear to survive into the 

 later strata of the Lower Ludlow. 



Lower Ludlow Beds. 



It is certain that we have yet much to learn with respect to 

 the Rhabdophora of the Upper Wenlock beds ; for none of the 

 forms enumerated above appear to survive into the Lower 

 Ludlow formation. In certain localities, however, these 

 Lower Ludlow beds are prolific in Graptolites, especially M . 

 Salweyiy Hopk., M. leintwardinensisy Hopk., M. Nilssoni } 

 Barr., M. bohemicus, Barr., M. scanicus, Tullberg, many of 

 which are present also in the highest zones of the graptoliti- 

 ferous rocks of Scania and in corresponding strata in Bohemia 

 and France. 



[To be continued.] 



