Winchell.] 4Ub [Mayti 



Of Nautili we are acquainted with 13 species from the Marshall group. 

 Of these, 11 or 12 belong to the section characterized by longitudinal fur- 

 rows and angulations and an open umbilicus, for which Messrs. Meek and 

 Worthen have proposed the sub-generic name Trematodiscus. 



Remarks similar to the foregoing could be oifered in reference to the 

 geological affinities of various other genera represented in the Marshall 

 group — as Platycrinus, Forbesiocrinus, Zeaerinus, Pterinea, Posidonomya, 

 Pinna, Maerodon, 8oUn and certain forms of Spirifera, Bellero-pTion, Or- 

 thoeeras and Goniatites. 



Such are the leading characteristics of the fauna of the Marshall group 

 which indicate its affinities with the Carboniferous system of Europe and 

 America. 129 To sum up: we tind 12 species identified with fossils from the 

 Carboniferous rocks of America; 12 species which extend from the Mar- 

 shall strata upwards into the base of the Burlington Limestone at a point 

 where the two formations rest in juxtaposition; 9 sj)ecies identified with 

 fossils from the Carboniferous rocks of Europe; 32 species whose ana- 

 logues recur in the higher Carboniferous rocks of America; 44 species whose 

 analogues recur in the Carboniferous rocks of Europe; 10 generic or sub- 

 generic forms largely represented, which characterize pre-eminently the 

 Carboniferous system, besides numerous other genera and species whose 

 affinities point rather to Carboniferous than to other strata. 



Two yeaxs ago, (Aug. 1866,) during the meeting of the American Asso- 

 ciation at Buffalo, a discussion incidentally arose as to the paleontological 

 relations of the Marshall group, in which on the one hand, it was claimed 

 that it presented "a Carboniferous aspect;" while on the other hand the 

 question was asked, "what is meant by a Carboniferous aspect?" and the 

 remark was added: "I don't know what you call a Carboniferous aspect." 

 I turn now to the citation of facts, of which I have just presented a sum- 

 mary, and reply: " That is what I mean by a Carboniferous aspect." 



To answer this question in other words, let me quote the language of a 

 distinguished American paleontologist. '3° " We have a right to contend, 

 therefore, for the existence of the Carboniferous system at any point 

 where we can find a continuation of the genera Pentremites, Productus, 

 Goniatites, iCijrtoceras, Discites) Naittilus and the ganoid fishes, i^i I con- 

 tend that this is the legitimate conclusion, or else the Carboniferous system 

 is subordinate to the Devonian." That is in principle exactly what I 

 contend for. It was in that school, too, that I received my teaching. 



VI. The Fauna of the Chemung Group presents a Devonian As- 

 pect. 

 In the further prosecution of this discussion it would be appropriate to 



129 The strata of the Marshall group probahly correspond to the " yellow sandstone" of Ireland 

 and the Westphalian schists lying at the base of the Carboniferous system. 



"0 Hall : Foster & Whitney's Rep. Lal^e Sup. Land Dist II, 308. 



131 May we not say that the Devonian is distinguished from the Silurian by the advent of these and 

 other types, while the Carboniferous is characterized by their great expansion ?— this being indi- 

 cated by the great multipUcation of species, the increased richness of ornamentation, the extrava- 

 gant development of certain features, and sometimes by unusual bulk. Carboniferous tj'pes in the 

 Devonian Age were, in skue-nse, prophetic faunas, or "colonies"— to employa phrase from Barrande, 

 used in reference to the Primordial Zoneof the environs of Prague. 



