77 



Mohawk river. The specimen in my cabinet, from 

 which our cast was made, is from that place. 



The Cryptolithus Tessellatus occurs also in the 

 limestone which, according to Dr. Bigsby, overlays 

 the sandstone in the island of Montreal. At most of 

 its localities, it is associated with the Isotelus, the 

 Calymene, and with several species of Asaphus. The 

 Cryptolithus, which is entirely destitute of eyes, being 

 thus found with the oculiferous species, is an inte- 

 resting fact, and controverts the opinion of Professor 

 Wahlenberg, that the trilobites, which are without 

 eyes belong to a geological epoch more ancient than 

 those which are furnished with oculiform tubercles. 

 That organic remains furnish us with the most satis- 

 factory evidence of the identity or dissimilarity of 

 certain formations, is a disputed point with some 

 geologists* It cannot reasonably be doubted, that 

 new and isolated facts have been made the basis of a 

 too hasty generalization. On this subject Count 

 Rasoumowsky makes the following remarks: " Les 

 divers gisemens des Trilobites ne me semblent pas 

 non plus pouvoir etre determines avec quelque pre- 

 cision. M. Brongniart parait admettre que les trilo- 

 bites aveugles ne se trouvent que dans de tres an- 

 ciennes formations dans des schistes et des calcaires 

 de transitions; mais nous avons clonne la descrip- 

 tion d'un trilobite [without eyes] des bords de la 

 Yaousa pres de Moscow, qui n'appartient certaine- 

 ment pas aux . formations de transition, ce qui me 



* See Eclectic Review, for July, 1832. 

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