STUDY OF THE GRAPTOLITES. 231 



1849. J. Hall stated the occurrence of twenty species of graptolites 

 in the Lower Silurian rocks ; two other species having been found in the 

 Clinton formation* [Proceedings of the Amer. Assoc, foi the Advancement 

 of Science, 1849, p. 351). 



1850. J. Barrande published a memoir upon the graptolites of Bohe- 

 mia, describing seventeen species of Graplolithus, of which fifteen were 

 new ; a new genus, Rastrites, with four species ; and the genus Retiolites, 

 with one species. These are all placed among the Polypi. All of these 

 species, except one, are found in the Upper Silurian ; four of them occur 

 in the colonies of the inferior division, and pass upward to the superior 

 beds ; while one species is restricted to the lower division. M. Barrande 

 has given in this memoir a resume of the geographical and geological 

 distribution of the graptolites in the different countries of the globe. 



1850. Prof. M'CoY described three species of graptolites, proposing 

 the name Diplograpsus for those with a double series of cellules. He 

 proposed also the generic name Protovirgularia for a zoophyte which he 

 refers to the Grorgoniadse, but which may perhaps belong to the Grap- 

 tolitidaB {Annals and Magazine of Nat. Hist., Vol. vi, 2nd series, 

 pp. 270-272). 



1850. Prof. Harkness described the graptolites found in the blaek 

 shales of Dumfriesshire, recognizing two species of Rastrites and ten 

 species of Graptolites [Quar. Jour. Geol. Soc, Yol. vii, pp. 59-65, pi. i). 



1851. Prof. M'CoY published descriptions and figures of graptolites 

 from British palaeozoic rocks, adopting the name Diplograpsus for the 

 species with two ranges of cellules. Of fifteen species which he described, 

 eleven are identified as those of preceding authors, and three of these 

 are recognized as American species {British Palceozoic Fossils, pp. 3-9, 

 PI. 3 B). 



1851. Dr. H. a. Prout described a graptolite, G. hallianus [=^ Den- 

 drograptus], from the Potsdam sandstone of the St. Croix River {Am. 

 Journal Science [2], Vol. ix, p. 187). 



1851. Edward Suess published descriptions of Bohemian graptolites, 

 reproducing nearly all of those described by Barrande, recof^nizing 

 several other known species, and describing nine new species. He pro- 

 posed the name Petalolithus as a substitute for Diprion = Phyllograptus 

 {Naturwissenschaftliche Abhandlungen, Vierter band, pp. 88-134, pis. vii, 

 viii, and ix). 



1851. J. W. Salter described G. tenuis, Portlock, and G. hullatus 

 = G. pristis'?, from the Silurian rocks of Scotland {Mwchison, Silurian 

 Rocks of Scotland, Quart. Jour. Geol. Soc, Vol. vii, pp. 173 and 174). 



1851. Christian Boeck : Bemcerkinger ajigaaeiide Graptolitherjie ; or, 



1851. ScHARENBERG, TJeher Graptolithen (cited by Geinitz; work not 

 seen by the writer). 



* This number of twenty speciee included some forms known, but not at that time 

 described. 



