82 WINCHELL AND MAECY ON FOSSILS FROM THE 



Our own investigations in the Chicago limestone which are the first to bring into 

 prominent notice this interesting locality seem to confirm, beyond all controversy, Mr. 

 Worthen's opinion of the age of the rock, as the following table will show ; and by estab- 

 lishing, through numerous identifications, given below, its parallelism with the Racine lime- 

 stone, admitted to be equivalent to the Leclaire limestone, it becomes geologically 

 demonstrated that all these limestones occupy a position in the Niagara group of New 

 York. 



But with which member of the group shall they be synchronized ? Our own identifications 

 tend to show a relationship with both the Niagara limestone and the Niagara shale ; of those 

 species, however, which, at the East, occur in the Niagara shale, it will be observed that 

 some, as Slrophomena rhomboidalis, Atrypa relicularis, Spirifera crispa, JS. radiata, Meristella nitida, 

 and Rhynchonella mglecta, are species which enjoyed either a great geological or great geo- 

 graphical range, or both together, and are thus proved to have been wanting in that sen- 

 sibility to geological variations which is requisite in fossils relied upon for stratigraphical 

 determinations. The same may perhaps be said of Caryocrinus ornatus and Lozonema subulata. 

 Of the others, the Poli/zoa may be regarded as only provisionally identified. There is left, 

 then, no strong bond of alliance between the Chicago limestone and the Niagara shale, ex- 

 cept the prevalence of crinoidal remains in both. But it will be noticed that we have been 

 unable to identify any species except Caryocrinus ornatus ; so that, admitting the alliance 

 shadowed forth by the presence of the crinoidal type in considerable force, we have a 

 much stronger affinity established with the Niagara limestone by the identification of sev- 

 eral species of true corals, as well as by the abundance of individuals of this type. For the 

 present, therefore, it seems to us that the Chicago, Racine, and Leclaire limestones exhibit a 

 satisfactory affinity with the Niagara limestone of New York. 



We have detected in the Chicago limestone no less than eighty-two species, of which 

 thirty-nine seem to be hitherto undescribed. If we add to these the few additional species 

 described by McChesney, from the same locality, we find that a single quarry has furnished 

 not less than eighty-seven species, another evidence of the abundance and variety of life 

 which teemed in the paleozoic seas. 



None of the Gasteropoda or Cephalopoda have been identified with New York species. 

 Of the identifications with New York species, the corals are all (except Pctraia calicula) 

 from the Niagara limestone, and the mollusks (including Bryozoa) are all from the Niagara 

 shale. 



It is noticeable that we do not find in our collection any specimens of HeliolUes, Eucalyp- 

 tocrimis decorus, Orthis elegantula, Spirifera nm/arensis, Pentamcrus oblongm, Rhynchonella cmieata, 

 or Calymene. 



Of the old species recognized by us, all have been described from the Niagara group of 

 North America. Loxonema subulata Conrad, was, however, originally described from the 

 Clinton group of New York, but has been identified in the Niagara group of Canada West, 

 as well as at Chicago. The geographical distribution of these species in some of the North- 

 western States, Canada West, and Europe, is presented at a glance in the following table : 



