HISTORY OF RESEARCH. civ 



and Nicholson (1895, as extended by Elles 1898) are adopted, and a compre- 

 hensive table is appended, illustrating the author's " Suggested Phylogeny of the 

 American Graptolite Axonolipa." 



In dealing with the geological range of the Graptolites Ruedemann summarises 

 in brief the far-reaching results already arrived at on both sides of the Atlantic by 

 previous graptolithologists, and combines them with the main results of his own 

 researches in a general " Correlation Table " of the Upper Cambrian and Lower 

 Ordovician formations of Scandinavia, Great Britain, Canada, and New York. In 

 calling special attention to the long-accepted generalisation of the almost world- 

 wide distribution of the same (or a large percentage of the same) characteristic 

 genera and species in corresponding zones, he argues that while there appear to 

 be some evidences of a local nature accordant more or less with the four theoretic 

 Lower Palaeozoic " provinces " of Freeh and others (deduced from the geographical 

 distribution of the Trilobita, Brachiopoda, etc.), yet there are other facts entirely 

 at variance with the distribution of the land and water areas as they can be 

 constructed for the Lower Siluric (Ordovician) age from the study of the littoral 

 faunas. His remarks are illustrated by a world-chart. 



As respects the mode of existence of the Graptolites, Ruedemann agrees with 

 those who regard the majority of the genera of the Dendroidea as being perma- 

 nently attached to rocks or growing sea- weeds in the littoral regions, thus forming 

 a part of the marine benthos of their time ; while the majority of the Graptoloidea 

 were probably attached to sea-weeds alone, and shared their fate, whether re- 

 maining permanently moored to rocks or the sea-floor off-shore, or drifting (like 

 the modern Sargassum) as pseudo-planlcton far and wide over the surface of the 

 deep seas. Some forms, however, and notably those arranged in stellate groups 

 Rudemann considers, had possibly attained a holoplanktonic stage of existence 

 corresponding with that of the Siphonophora of the present day. 



In the Descriptive Section of the volume Ruedemann gives diagnoses of some 

 forty species of Graptolites occurring in the New Y'ork formations dealt with. 

 These are arranged by him in six families, viz. 1, Dendrograptidae (Roemer) > 

 2, Dichograptidse (Lapw.) ; 3, Coenograptidas (nov.) ; 4, Phyllograptidse (Lapw.) ; 

 5, Diplograptidas (Lapw.) ; and G, Climacograptidae (Freeh) ; and seventeen 

 genera, of which two, Sigmagraptus and Strophograptus, are new. The following 

 are the new species described : Dendrograptus (?) succulentus, D. fluitans, Ptilo- 

 graptus tenui-simus, Dictyonema furciferum, D. rectilineatum, Destnograptus 

 intricatus, Goniograptus gometricus, G. perflexilis, Temnograptus Noveboracensis, 

 Bryograptas LapwortM, B. pusillus, Tetragraptus Clarkei, T. Wocdi, T. taraxicum, 

 T' Pyg ma eus, T. lentus, Didymograptus cuspidatus, D. Ellesi, D. Tornquisti, 

 D. spinosus, D. forcipiformis, I), incertus, Sigmagraptus precursor, Strophograptus 

 trichomanes, Diplograptus laxus, D. longicaudatus, Glossograptus hystrix, G. 

 echinatus, Glimacograptus spongens 



