(•11 



BRITISH GRAPTOLITES. 



sixteen. All these are characterised by a large disc, the development of which 

 he traces. 



Two specimens of a form doubtfully referred to Dichograptus Mil<>xi are 

 figured, and fragments of Dendrograptus (?), Pleurograptus (?), and Ccenograptus (?). 



1882. 



Hopkinson, 



'On some Points in the 



Morphology of the 



Rhabdophora or true 



Graptolites," ' Ann. 



A paper by Hopkinson on the " Morphology of the 

 Rhabdophora," previously read before the British Association 

 in 1881, was published in full in the early part of 1882. 

 In this paper he figures and describes a specimen of Tetra- 

 graptus serra, indicating the presence of an internal ridge and 

 Mag. Nat. Hist.,' ser. 5, constriction at the base of each hydrotheca. 



vol> 1X - He concludes (1) "that in certain Graptolites the calycles 



seem to be completely cut off from their supporting perisarc, this appearance 

 being due to a constriction, or the presence of a partially dividing ridge," and (2) 

 that "in these same forms there are at least constrictions in the perisarc, dividing 

 it into sections, from each of which a calycle is produced." 



He holds that these phenomena show that the calycles of the Graptolites are 

 true hydrotheca?, and that the Graptolites are the " Palaeozoic representatives of 

 the recent Hydrophora." 



Three stratigraphical papers in which Graptolites are referred to also appeared 

 during the year 1882. 



The first was by Marr, who gave a generalised account 

 of his visit to the classic localities of the Cambrian and 

 Silurian rocks of Scandinavia, summarised the discoveries of 

 the Scandinavian geologists, and correlated anew the fossil- 

 bearing formations with the British and Bohemian deposits. 

 He notes the Graptolite zones previously correlated by earlier 

 observers, and gives a full list of the Graptolites from the 

 Eetiolites beds of Bornholm. 



The second was by Schmidt, who gave a description of 

 the " Silurian (and Cambrian) Strata of the Baltic Pro- 

 " On the Silurian (and vinces of Russia," and their successive fossiliferous zones 

 Cambrian) Strata of as developed by himself during a lifetime of research. He 

 the Baltic Provinces of compares them with those of Scandinavia and the British 

 'Quart. Journ. j s ] es an( j fixes the exact horizons of Dictijonema and Phyllo- 

 graptus in the sequence in the Baltic Provinces. 



The third was by Lap worth, on " The Girvan Succession 

 in South Scotland," in which the value and reliability of the 

 Graptolites as " zone fossils " were again demonstrated, by the 

 discovery in the Girvan district of the same series of Grapto- 

 litic zones in the same order as in the previously described 

 Moffat area, notwithstanding the great differences between 



1882. 



Marr, 



" On the Cambrian and 



Silurian Rocks of 



Scandinavia," ' Quart. 



Journ. Ceol. Soc.,' 



vol. xxxviii. 



1882. 

 Schmidt, 



Geol. Soc.,' vol. xxxviii. 



1882. 

 Lapworth , 

 "On the Girvan Suc- 

 cession," ' Quart. 

 Journ. Geol. Soc.,' 

 vol. xxxviii. 



