Wincliell.] "'^^ [May6, 



3. Orthis resupinata de Kon. ranges from the Devonian into the Carbon- 

 iferous system both in Europe and America. 



4. OrtMs TJdemei, White, from Iowa, is reported by Professor Hall as 

 identified in the Chemung of New York. 



5. G/ionetes Logani Nor, and Prat, is also reported by Professor Hall 

 occurring in the Tully Limestone. I have heretofore expressed my dis- 

 sent from this identification. "^ I pronounced the New York species dis- 

 tinct before being informed of its geological position or locality. It pre- 

 sents a series of concentric rugosities or wrinkles which extend both across 

 the ribs and the intervals between the ribs, while in (7. it>5'a;ii the rugosi- 

 ties are feebler, and are confined to the crests of the ribs. 



0. Strophomena rJio'niboidaUs,W aM, has a range even greater than that 

 of 0. resupinata. 



7. Spirifera inucronata Con., found in the Chemung of Steuben County, 

 N. Y., was doubtfully identified in Missouri. Not having seen the Mis- 

 souri specimens, I would be strongly inclined to suspect that they belong 

 rather to S. extenuata, or some related species. 



8. Ctenodonta bellatula, Hall, sp. of the Hamilton group of New York, 

 has also been doubtfully identified in Missouri. 



A few additional species had been provisionally repo .-ted identical with 

 Chemung forms, but as already stated, a direct compa -ison of the species 

 suspected to be identical has induced me to abandon the identification in 

 every instance. We have then no unquestioned identifications with species 

 from rocks as old as the Chemung, except in the case of Orthis resupinata 

 and Strophomena rhomhoidalis, and perhaps Orthis Thiemei. It is fair to 

 presiune that the forms of Strophomena rhomboidalis, occurring as high as 

 the Marshall group, will yet be distinguished from the Silurian forms by 

 appreciable characters, as has been done recently in respect to the forms 

 of Atnjpa reticular is. '^^^ The different expression of the Marshall forms 

 has already been remarked. This species, so abundant in the Marshall 

 period, existed in the Lower Silurian, and appears to have attained its cul- 

 mination in the Upper Silurian. There is an improbability that the same 

 species, after having once undergone a decline, should attain a second cul- 

 mination in seas swarming with species and types of a much later period. 



I think it will be admitted that tlie palajnotological corresi^ondence be- 

 tween the Marshall and the Chemung strata is extremely meagre. We 

 know four hundred and fifteen species from the strata of the Marshall 

 period, of which 138 come from Oliio, a State almost in continuity with 

 the State of New York. We know probably 100 or 150 species from the 

 Chemung of New York; and yet we are able to identify scarcely a single 

 characteristic species with the types of the Marshall group. This state of 

 the facts looks very unfavorable to the attempt to parallelize the Marshall 

 and Chemung. 



I proceed now to point out the specific facts bearing upon the relation 

 subsisting between the Marshall fauna and that of formations in Western 



118 Proc. Acad. Nat. Sci. Phil. July, 18fi.j, p 116. 



ii!" Whitfield : observations on the internal appendages of the genus Atrypa, IXfiO- 



