ON THE STOCKDALE SHALES. 



709 



In the Lake-district : — 



1. Bi'plograjpius acuminatus, common. 



2. D. vesicidosns, common. 1 

 J), acuminatus has disappeared, J 



3. Monograptus gregarius, common, 1 

 Di'plograptics vesiculosus, very rare. J 



4. Lack of abundance of Petalograptus 



cometa. 



5. Abundance of Monograptus spinigerus. ) 

 1 sdecimen of M. gregarius. J 



6. Abundance of Eastrites maximus. 



In the Moffat area : — 

 D, acuminatus, common. 

 D. vesiculosus, common. 

 D. acuminatus has disap- 

 peared, 

 r M, gregarius, common. 

 \ D. vesiculosus, very rare. 

 Abundance of P. cometa. 



Abundance of M. sjpinigerus. 

 Absence of M. gregarius. 

 Abundance of E. maximus. 



Furthermore, our divisions of the Middle SkelgiU Beds are, at any 

 rate partially, suggested by an examination of the mode of occurrence 

 of the Graptolites in the gregarkis-zone of Scotland. Prof. Lapworth 

 states that in his district " Monograijtus Sandersoni (Lapw.) and 

 M. fimhriatus (Nich.) are unknown above the central line" of the 

 gregaynus-zone. In our country they are found in the fimhriatus- 

 zone, but not above it. Again, " Monograjptus triangularis (Harkn.) 

 occurs only in the neighbourhood of the nodule-band " which is near 

 the centre ; with us it is only found in iho, fimhriatus-zone. Lastly, 

 " neither Rastrites peregrinus nor Diplograptus vesiculosus reach the 

 summit of the group." We find the former confined to the jimhri- 

 atus-zone, and the latter rarely occurring in it, and not higher. 



Passing now to the Browgill Beds, we find at first sight less 

 striking resemblances in the more minute subdivisions ; but this is 

 partly due to the reference of the peculiar Monograptus discus to 

 M. turriculatus, Barr., and the inclusion of Monograptus jjandus 

 with M. priodon in the published lists. Prof. Lapworth, in his 

 paper on the '* Geological Distribution of the Rhabdophora," p. 41, 

 gives a list of fossils from the Gala group. Twenty-one species are 

 there enumerated, of which twelve have been discovered by us in 

 the Browgill Beds, and of these twelve only two pass down into the 

 Skelgill Beds, and these only occur in the upper group. We cannot 

 find any record of the separation of the turriculatus-'he^^ as a distinct 

 zone ; they undoubtedly form such in the Lake- district, and the two 

 forms Monograptus turriculatus, Barr., and Rastrites distans, Lapw., 

 appear to be strictly limited to it in that area. 



The fossils of the zone of Monograptus crispus are mostly found 

 in the Gala group, and M. exiguus is a very common form in the two 

 areas. In Prof. Lapworth's paper on " The Girvan succession " * the 

 equivalents of the Gala group, the " Crossopodia-^rovi^^'^ are divided 

 into Lower Penhill Shales with Monograptus exiguus &c.. Middle 

 PenhiU flags and grejwackes, in which the Graptolites of the pre- 

 ceding beds recur, and Upper Penhill muds tones, or G^ra^/ce-beds, with 

 Cyrtograptus Grayce and JRetioUtes Geinitzianus. It has already 

 been pointed out that although we are unable to separate the Grayce- 

 beds and the beds wdth Retiolites Geinitzianus from the beds of 

 our cnspws-zone, we have found that they are limited to the upper 



* Q. J. a. S. vol. xxxviii. p. 652. 



