

226 Parallelism of the Paleozoic Deposits 



higher than those which contain Pentarnerus oblongus. In Bo- 

 hemia, according to Mr. Barrande, the C. insignis occurs in an 

 analogous position, that is to say. in the middle division of the 

 upper Silurian stage. # 



Sphmrexochns mirus, Beyr. — This very remarkable species is 

 found at Springfield, Ohio, and at Madison, Indiana. At the first 

 locality it is associated with the Pentarnerus oblongus ; in the 

 second, it is found at the summit of the great cut through which 

 the railroad passes in the limestones which are at the junction of 

 the two great stages of the Silurian system. 



In Bohemia it is also at the base of the upper Silurian stage 

 that this species has been discovered. The museum of Dudley 

 possesses a specimen found in the limestone of that city. In 

 Sweden it descends into the lower Silurian stage, for under the 

 name of Calyrnene clavifrons, Hisinger has figured the head ot 

 a trilobite from Furudal in Dalecarlia, which appears to us very 

 like the species in Bohemia. Nevertheless if the figure is exact 

 there must be some difference. 



[We have copied entirely the remarks of M. de Verneuii upon 

 the fossil fishes and trilobites common to the two countries. 

 For the remainder of the species cited by him we refer to the 

 table appended, mentioning only those on which we make some 

 comments. The absolute identity of species and similarity ol 

 position of many of the trilobites in the two countries is very 

 remarkable, and much more conspicuous than in any other family 

 of fossils. It is no less an interesting fact, that in nearly every 

 important stage in the geological succession which we recognize 

 in New York, there is almost a complete representation or re-crea- 

 tion of the types of the earlier period. Some forms are gradually 

 lost it is true, while the principle or idea prevailing in those may 

 be recognized to some extent in others. We may cite some 

 examples. 



The species of Trilobites with equal or nearly equal extremi- 

 ties, common in the forms of Ilteenus, Isotelus and Asaphus, are 

 represented only by Bumastis in the Niagara group where this 

 form ceases. The genus Lichas which first appears in the Tren- 

 ton limestone, appears in the Niagara group in the form of the 

 large and beautiful L. Boltoni. A very similar species occurs in 

 the Delthyris shaly limestone and a fourth in the Corniferous 

 limestone. In these four distinct and widely separated stage* 

 the type is easily recognizable even from fragments, and the spe- 



* [The head of this Trilobite has been found at the hase of the Niagara or upper 

 >art of the Clinton group at Lockport, and in the shale of the Niagara group at 

 Rochester. This fossil is clearly a species of the genus Ceraurus of Green, WDicB 

 rijmie has precedence over that of Cheirurus. The C. insignis as it occurs in 

 New York, bears much general resemblance to the C. pleurexanthemus. The latter 

 must be regarded as the typical form of the genus.— J. H.] 



