



22S Parallelism of the Palceozoic Deposits 



elsewhere said, we believe the beds containing this fossil in Eu- 

 rope will be found to belong to the upper stage. Thus far no 

 species of Pentamerus is known in the lower Silurian stage, and 

 we feel much confidence in the theoretical views which we en- 

 tertain regarding the progressive development of types which 

 would not admit of such a form in the lower stage. 



Spirifer sulcatus, Dalm., (Delthyris decemplieata. Hall). 

 " This species occupies at Lockport the same position as in the 

 island of Gothland." We have no doubt of the identity of our 

 species with the European one after having had an opportunity 

 of comparing authentic specimens. 



S. crispus, Dalm., (D. staminea, Hall). — This species which 

 is frequently confounded with the last, is entirely distinct, and is 

 also identical with the Swedish species. 



" S. bilobus, Linn., sp. (S. sinuatus, Sow., $. cardiospermifor- 

 mis, His. : Delthyris varica, Conrad.)" — " This remarkable little 

 species of the Wenlock stage is found in the equivalent rocks of 

 Rochester, New York \ but it is even more abundant in more 

 recent beds, that is to say, in the Delthyris shales ; it is to this 

 one that Mr. Conrad has given the name of D. varica, which is 

 distinguished from the other by a shorter hinge, by its general 

 form being more enlarged and by a more profound sinus. A care- 

 ful comparison of the two varieties with the S. bilobus of Europe 

 induces us to reunite them." 



We regret to feel compelled to differ from the opinion of so 

 careful an observer as M. de Verneuil, but in this case we cannot 

 hesitate to pronounce the two varieties of form in question, very 

 distinct species. The Niagara species is doubtless identical with 

 the Swedish one, while the other differs in being much larger and 

 having both valves convex. Of the D. varica we have some 

 thousands of specimens and even in the smaller ones, correspond- 

 ing to the Niagara species in size, we find a marked contrast. 

 The differences between these two species of the two stages is 

 equally as great in proportion to the size of the specimens, as be- 

 tween the Delthyris crispa of the Niagara group and the D. cy- 

 cloptera of the Delthyris shale, or between I), sulcata of Niagara 

 and D. of the Delthyris shale. 



Orthis hybrida, Sow. — The species occurring in the Niagara 

 group and the one in the Delthyris shale are quite distinct, as we 

 shall be able to prove by specimens and figures. 



Favosites gothlandica, (Goldf sp.)— We are not confident as 

 to the wide geological range of this species, though it probably 

 occurs in the Silurian and Devonian systems. We have neverthe- 

 less been unable to find a characteristic specimen in the Clinton 

 and Niagara groups ; those which we have long referred to it prov- 

 ing to belong to an entirely distinct genus. There is however 

 a species of Favosites in the Niagara group, but it occurs in small 

 irregular forms and it is not easy to decide its specific relations. 









