Raymond: liRAciiiopoDA and OsruAroDA or ihk Cha/y. 223 



Zone fvi («fc Annals CAUNEdUi Museum. Xol. Ill, p. 517), 718 

 feet ;ib()\e tlie base of the formation. In iliis zone, the specimens 

 are rare, and all arc without fold and sinus, but correspond in all 

 respects to the shell ot Cuninrotxchia plena in the neanic stage. In 

 the next /one, 7J1) feet abo\e the base, the species suddenly becomes 

 abundant, but all the specimens are small, with numerous plications. 

 Specimens are fairly common in the succeeding forty feet of strata, 

 and the species becomes constantly more variable in the size and 

 number of plications, until in the layers around Cystid Point (Zones 

 37-39, at 767-789 feet above the base of the formation) we find the 

 acme of variation. At this locality may be found all the varieties of 

 Canuiroteechia plena that are found in any of the strata higher or lower, 

 and, while the species is more abundant in some of the later beds, its 

 characters become more fixed, and there is not so great a variety of 

 forms. 



Locality. — This species is very common in the upper part of the 

 Chazy at X'alcour Island, Chazy, and other localities in northern 

 New York, at South Hero and elsewhere in Vermont, and in the 

 Aylmer formation in the Ottawa Valley. The specimens here figured 

 are in the Carnegie Museum. 



7. Camarotoechia orientalis (Billings). 



(Plate XXXIII, figures 19-22, 24-33.) 

 Rhynchonella orientalis Billings, 1859. Canadian Naturalist and Geologist, Vol. 



IV, p. 443, fig. 21. 

 Rhynchonella orientalis Billings, 1863. Geology of Canada, p. 126, fig. 57. 



It was suggested by Sir William Logan (Geology of Canada, 1863) 

 that Camarotoechia orientalis was probably only a variety of Camaro- 

 toechia plena. Considering the variability of the latter species it is 

 possible that Camarotoechia orientalis arose from it by the checking 

 of the plications at an early stage, while the fold and sinus continued 

 to maturity. In this connection it should be noted that the two species 

 do not seem to occur together. At the Mingan Islands and at St. 

 Martin Junction near Montreal, where Camarotoechia orientalis is 

 abundant, Camarotoechia plena does not occur. On the other hand, 

 Camarotoschia plena is very abundant at Valcour Island, Chazy, and 

 South Hero, but no specimens of Camarotoechia orientalis have been 

 found in that region. In all these localities Camarotoechia is accom- 

 panied by an abundance of Ilebertellas. At St. Martin Junction,^ 



