468 JYotices of Memoirs — Yorhshlre Polytechnic Society. 



Of the allied forms, all the genera of the so-called dendroid grap- 

 tolites, so characteristic of the Quebec group, are present in the St. 

 David's beds. Ftilograptus is represented by two new species, and 

 Dendrograptus by five species, three of which — D. divergens. Hall, 

 D. flexuosus, Hall, and D. striatus, Hall — are at present only known 

 to occur elsewhere in the Quebec group, the other two being new. 

 Callograptus is also represented by five species, three — C. elegans, 

 Hall, C. (?) diffusus, Hall, and G. Salteri, Hall — being Quebec forms, 

 and two being new ; and lastly, of Dictyonema but one species, which 

 is new, has been found. Many obscure impressions referred to the 

 genus Betiolites also occur, one species seeming to agree perfectly 

 as far as its state of preservation allows of comparison with Prof. 

 Hall's figures, with his B. ensiformis of the Quebec group. Another 

 appears to be distinct from any species yet figured. 



The Graptolites and their allies are now thus known to be re- 

 presented in the Arenig rocks of St. David's by nine genera and 

 about twenty-two species. "^ Of the true Graptolites three genera — 

 namely, Tetragraptus, Loganograptus, and PTiyllograptus — are ex- 

 clusively confined to the horizon of the Quebec and Skiddaw groups. 

 The remaining genus, Bidymograptus, is represented in higher rocks 

 by but two species, D. Murchisoni and D. serratulus. The former 

 occurs in the Lower Llandeilo, at Abereiddy Bay, near St. David's, 

 and at Builth ; and the latter in the Hudson Eiver group (Caradoc) 

 of New York. It has also been recorded from the Skiddaw slates. 

 With these exceptions Bidymograptus is exclusively an Arenig genus 

 occurring in rocks of this age in Canada, Cumberland, and Shrop- 

 shire. The four genera of dendroid Graptolites have a more extensive 

 range, Dictyonema lasting from the Cambrian to the Devonian period, 

 but until now they were only known to occur together and in any 

 abundance in the Quebec group of Canada. 



During, however, a recent visit of the Geologists' Association to 

 Ludlow and the Longmynds, the author had found, at Shelve, in the 

 lower part of the Arenig rocks, underlying the great mass of the 

 Llandeilo, a Graptolite zone, in which these four genera are repre- 

 sented by species, some of which are identical with, and others 

 nearly allied to, those in the St. David's beds and in the Quebec 

 group of Canada ; these beds, and also the Skiddaw slates of Cum- 

 berland, the equivalency of which with the Quebec group has 

 already been shown by Prof. Nicholson, being therefore of Lower 

 Arenig age. 



IV. — Proceedings of the Geological and Polytechnic Society 

 OF THE West Eiding of Yokkshike. New Series, Part I. 

 1871-72. 



ME. L. C. MIALL read a paper on the Contortion of Eocks.^ 

 He exhibited photographs showing contorted Limestone 

 Beds in Draughton Quarry, where solid layers of rock, a foot or 

 two in thickness, have been bent into the figure of an inverted W. 



^ See Geol. Mag. for November, 1869; also Popular Science Eeview, January, 

 1872. 



