c.\ 



BRITISH GRAPTOLITES. 



the presence of two others, i. e. the Dictyonema sociale zone and that of the 

 Llandeilo, lie regards as yet problematical. 



j) 0( j ae Dodge described a few species of Graptolites found by 



•• Some Silurian Grap himself in Maine in beds of Norman's Kill age. They include 



tolites from Northern Helicograptus gracilis, Dicellograptus sp., Diplograptus sp., 



Maine," ' Amer. Journ. Cryptograptus marcidus, and Glossograptus spinulosus. 

 Sci.,' vol. xl. 



1890. 



Gurley, 



" Geological Age of the 



Graptolite Shales of 



The geological age of the Graptolite shales of Arkansas is 

 discussed by Gurley in a paper published in 1800. He 

 recognises two horizons — the Trenton and the Calciferous. 

 The latter, he considers, corresponds to the Point Levis beds, 



Arkansas and some new the former to the upper part of the Norman's Kill fauna. 



Species of Graptolites," The stratum mar l ccc j out by t l ie l atter distinctive fauna is 



. '" ', termed by him the " Dicelloqraptus zone," and is divided into 



Arkansas J j ± 



(a) Lower Dicellograptus sub-zone with Ccenograptus gracilis, 

 and (b) Upper Dicellograptus sub-zone without Goenog. gracilis. The Arkansas 

 fauna thus corresponds to that of the Upper Zone. He describes four new forms : 

 Dicranograjitiis arkansasensis, Dicranog. Nicholsoni var. parvangulus, Diplog. 

 trifidus, and Dictyonema obovatum. Only two of the species are figured. 

 A complete list of the Graptolites obtained from Arkansas is also given. 



In 1890 Getz described a few specimens obtained (mainly 

 by Herrmann) from two distinct Graptolite horizons in the 

 Trondhjem district, corresponding the one to Upper Glenklin 



1890. 

 Getz, 

 " Graptolitforende ski 

 ferzouer i det Trondh- 

 jem ske," ' Nyt Mag. 

 for Naturvid.,' bd. xxxi 



or Lower Hartfell, and the other to the Birkhill. The Grapto- 



lites are poorly preserved owing to the cleavage of the beds, 



and it is impossible to identify more than Dicranograptus 



ramosus and Climacog. bicornis, but the author records in 



addition a species of Didymograptiis, Diplograptns, and Dicellograptus from the 



lower horizon. From the Upper Birkhill zone he figures M. cfr. convolutus, Mono- 



graptus Haiti and Rastrites sp. 



1890 

 „. , , ' „ The same year H. O. Nicholson recorded the existence of 



Nicholson, 11. (J., _ ^ 



" Note on the Occur- Trigoii.ogra.pttis eiisiformis in the Ellergill Beds of the Lake 



rence of Triyonograptus District, and also described a new variety of Didymograptiis 

 ensiformis, etc.," ' Geol. under the name D. r-fractas var. volucer. 

 Mag.,' dec. 3, vol. vii. 



Geinitz, in a paper published in this year, revised the fine 

 collection of Graptolites in the Dresden Museum, and gave 

 descriptions and figures of some of the species identified. He 

 retains all the genera and species of Graptolites originally 

 described by him, with the exception of Nereograptus. Very 



1890. 



Geinitz, 



' Die Graptolithen des 



k. Mineralog. Mus. in 



Dresden.' 



