Raymond : Thk Cha/\' Formation and its Fauna. 



561 



Alodiolopsis brriniisciila , 

 Modiolopsis parviiisiiihi , 

 Modiolopsis sotvteri, 

 Ctenodoiihi par7'idens, 

 Arcliinacclla / dcfoniiata, 

 Raphistoin a striatum , 

 RapJiistflina statu inciiiii , 

 Si •( ! I/'tcs i>il///igsi, 



Bathytinis angclini , 



Isoteliis sp. ind., 



Bcyri cilia clavi^^era , 



Beyrichia clavigera clavifracta, 



Pritiiitia sp., 



Isocliilina sp. 



Modiolopsis brei'iiiscnla, 

 Modiolopsis parviiisiiila, 



J^ap/i/stoi/ia staininctiiii, 



Orthoccras allitmctteiise, 

 Bathxunis a}i<^eiiiii, 

 /. (pcrditia 1 1 in \ gda I in 1 1 , 

 L/pt'rditia ca/iadc/isis, 

 Isocliilina Ottawa, 

 JsocJiilina aniiana, 

 Lcperditclla lalcllosa, 

 Priniitia loi^a/ii. 



These parallel faunal lists show that of the twenty-five species com- 

 mon in the Aylmer formation around Ottawa and Aylmer, seventeen 

 occur in the sandstone and fourteen in the limestone, six species 

 being common to the two divisions. In the sandstone the mollusca 

 l)redominate. They are represented by four species of pelecypods 

 and four of gastropods, while in the limestone there are only two of 

 the former and one of the latter, all three being species which come 

 up from below. In the sandstone the ostracods are not common, nor 

 are they sufficiently well preserved to be easily identified. In the 

 limestones, however, the ostracods are exceedingly abundant, some 

 layers being entirely made up of their shells. Trilobites are not 

 numerous, either in species or individuals. 



It has been suggested that the limestones of this formation should 

 be united with the Lowville limestone above, rather than with the 

 sandstone below. AMiile there is a considerable change of fauna 

 between the .sandstone and limestone, as is indicated by the above 

 lists, still the two faunas are intimately connected by six well-defined 

 species. On the other hand, none of the species of the Aylmer lime- 

 stone pa.ss up into the Lowville limestone. The transference, there- 

 fore, of this horizon from the Chazy into the Lowville is not borne 

 out by the faunas, the primary guide for stratigraphic determina- 

 tion. 



