OfJ'J AXNAI.S OF THE CaRXEGIE MuSEUM. 



Co/iipiirisD/i of the Chazy Fauna of tlie Othuoa Rei^ioii with the 

 Typical Fauna in the Lake Champlain Region. 



The most noticeable feature of the fauna of the Chazy in the 

 Ottawa region is the absence of the cystids, bryozoa and hydrozoa so 

 common in the regions of the typical Chazy. Farther, the small num- 

 ])er of species of brachio])0(ls and trilobites is in marked contrast to 

 the far greater variety found at Chazy and Valcour Island. On the 

 other hand ostracods are exceedingly abundant in the Ottawa Valley, 

 and usually rare in the Chamj)lain A^alley. 



Of species common to the two regions there are seven or eight : 

 Cainarotivchia plena, Caniarota'chia orientalis, Rafinesqiiina alternata, 

 Raplii stoma sta/ninei/ni, Rapltisionia striatum, Arcliiiiacclla ? deforntata, 

 Leperditia canadensis and Hel^ertella I'orealis. In the Champlain Val- 

 ley region Camarota'chia plena is found only in the upper 150 to 175 

 feet of the section, while the other species in this list have a more 

 extended range. The two species of Rapliistonia are usually found 

 more than 300 feet above the base of the section and are most common 

 somewhere about the middle. The range of Caniarota'chia orientalis 

 and Archinacella ? deforniata is not known. Rajinesi/uina alternata, 

 Hebertclla horealis, and Leperditia canadensis range all through the 

 section. 



Judging from the presence of Cainarotachia plena and the two 

 species of Raphistonia, the Aylmer formation would be correlated 

 with the upi)er part of the section at Chazy. That the whole of this 

 formation should be thus correlated is shown by the fact that Caniaro- 

 ta'chia plena occurs not only in the limestone member at the top of 

 the formation but also in the sandstones near the base. 



, CONCLUSIOXS. 



The Chazy fauna, as it is now known, consists of about 200 species 

 distributed among the classes as follows : Hydrozoa and Spongiae ? 13, 

 Anthozoa 3, Crinoidea 7, Cystoidea 10, Blastoidea ? 2, Vermes 2, 

 Bryozoa 10, Brachiopoda 30, Pelecypoda 23, Gastropoda 40, Cepha- 

 lopoda 15, Ostracoda 12, Trilobita 38, incert?e sedes, 4. 



This fauna shows a decidedly closer affinity with the fauna of the 

 Black River and Trenton formations of New Vork and Canada than 

 with the Beekmantown of the same regions.^'' Our knowledge of the 



■^^'The stron<^ Mohavvkian facies of the Chazy fauna suggests that the Chazy forma- 

 tion should be taken out of the Canadian, the IJeekmantowii and Chazy having very 

 little in common. 



