176 



REPORT — 1881. 



Mr. Lapworth's scrutiny before publication. He has gone over every one 

 of these notes critically, and, as his decision is adverse to my own views 

 (founded to a large extent upon facial resemblances), I cannot do other- 

 wise than bow to his dictum. ' If the Polyzoa and the Graptolithina 

 had a common ancestor — a view I have always been disposed to adopt 



myself it must have existed at an antiquity far more greatly removed 



from Silurian times than Silurian time is from our own ages ; for the 

 differences which then separated the two groups appear to have been 

 almost as gigantic in importance as those which divide the Hydrozoa and 

 Polyzoa of the present day.' 



For the purpose of comparison I append a list of the leading genera 

 of the Graptolites with the genera of Polyzoa found in the same foi-ma- 

 tions. 



Vertical Range of Gkaptolites, according, to Nicholson, Lapworth, and 

 Catalogue of Cambrian and Silurian Fossils, School of Mines. 



(N.) Nicholson. (S.M.C.) School of Mines Catalogue. 

 Genera onlj' given, with corresponding increase of Polyzoa. 



Oldhamia antiqua, Forbes ; O. radiata, Forbes (S.M.C. p. 8). 



JDiotyoneiiia spciale, Salter (S.M. p. 12), also in Tremadoc slates 

 (N.) 



Dichograptiis, Didymograptus, Tetragraptus, Climacograptus, 

 DiiDlograptus, Graptolithus, Eastrites, Dictyonema? Phyllo- 

 graptns, Graiitolithus (S.M.C. pp. 17-18), Trigonograptus, 

 Ptilograptus, Dendograptus, Callograptus, Dictyograptu.s 

 (Lap.) Polyzoa: Phyllopora.Ptilodictya (Lower Llandeilo), 

 Branching pol^'zoon (S.M.C. xo. 20), hardly distinguishable iu 

 form from Graptolithina, only it is calcareou.s. 



Didymograptus, Tetragraptus, Climacograptus, Diplograptus, 

 Dicranograijtus, Graptolithus, Eastrites, Dictyonema, Pro- 

 tovirgularia, Helicograptus, Pleurograptus, Dicellograptus, 

 Cyrtograptus (S.M.C. pp. 23-24). Polyzoa: Ptilodictya 

 and Fenestella ? n.p. (Ibid. p. 28). 



ClimacogTaptus, Diplograptus, Dicranogxaptus, Dendograptus, 

 Graptolithus (S.M.C.'p. 31). PoLYzoA : Berenicea, Fenes- 

 tella, Glauconome, Phylojjora, Ptilodictya, great increase of 

 species (Ibid. p. 44). 



No Graptolites in S. M. C, Climacograpsus one sp., Graptolites 

 pnodon, Bronn (Nich. Mono. pp. 97, 98). Polyzoa : Fenes- 

 tella ? Glauconome innexa, Phyllopora, Ptilodictya. 



GraptoUthvs j^nodun, Dictyonema (S.M.C. p. 69). Polyzoa : 

 Ptilodictya, Fenestella. 



Cladograptus, Cyrtograptus, Graptolithus, Eetiolites, Dictyo- 

 nema (S.M.C. p. 81). Polyzoa : Fenestella, Ptilodictya 

 (Stomatopora species. Vine). 



Graptolithus priodon, Bronn (S.M.C. p. 93), Graptolites colonos, 

 Eetiolites, Cyrtograpsus, Ptilograpsus (Nich. p. 98). Poly- 

 zoa : great increase of species, see list. 



Dendograptus, Graptolithus (S.M.C. p. 115). Four species 

 recorded both in Catalogue and the same by Nicholson. 



Graptolithus sp. recorded (S. M. Cat. p. 128). 



(L.) Lapworth 



Formation. 



Cambrian. 



Up. Lingula Flags. 



Arenig and Llau- 

 deilo. 



Up. Llandeilo. 



Caradoc. 



Lower Llandovery 



Up. Llandovery 

 Wenlock Shale 



Wenlock Limestone 



Lower Ludlow 

 Upper „ 



> Concluding remark in Mr. Lapworth's letter to me, May 16, 1881. 



