172 NEW YORK STATE MUSEUM 



of development of fold and sinus, rapidity of bifurcation of plications and 

 other minor and fugitive features. The material which was described by 

 Hall in Palaeontology of New York, volume 3, so far as it was derived 

 from the New York formation was not specially good and this is prob- 

 ably the reason of the endeavor to establish so many specific distinc- 

 tions therein. With the higrh arade material which has now been derived 

 from the Glenerie deposits it is not easy to find much basis for most of the 

 distinctions then made (R. pleio pleura, m u 1 1 i s t r i a t a, princi- 

 palis, o b 1 a t a, f i t c h a n a^. There are two pretty well defined specific 

 types one with coarse angular, few and simple plications, viz, R. b a r r a n- 

 d e i and the other with the plications more numerous and rapidly bifurcat- 

 ing. Billings identified with R. pliopleura the large shells from Gaspe 

 and we are disposed to continue this name, though specimens of just this 

 type are not familiar to us in the New York Oriskany. These Gaspe shells 

 are large and fine examples with highly convex dorsal valves, specially full 

 at the umbo, rather shallow ventrals, little if any trace of fold or sinus on 

 the first half of the valves and both broad and not abruptly flexed at the 

 anterior margin. In immature stages the shell has the aspect of R. o b 1 a t a 

 Hall. The surface striae are very numerous (100-150), much in excess of 

 those in the New York shells which rarely run above 70 and these are 

 increased by the rapid bifurcation with growth. 



There is so much uncertainty at present in regard to the specific values 

 in this group of shells that, though recognizing the departure in the shells 

 of the Grande Greve limestones we are disposed to retain for them the 

 term applied by Billings. 



Dimensions. Normal adults attain a size of about 55 mm in length 

 and 50 mm in width. 



Localities. The best and most abundant specimens have been found in 

 Dolbel brook and on the coast at Lehuquet's. 



Eatonia peculiaris Conrad 



Plate 29, figures r-13 



A t r y p a p e c u li ari s Conrad. N. Y. Geol. Sur. 5th An. Rep't. 1841. p. 56 

 Eatonia peculiaris Hall. Palaeontology of New York. 1859. 3:244, pi. 38, 



fig. 21-26; pi. 51, fig. 2; pi. loi, fig. 2; plate lOfA, fig. i 

 Eatonia peculiaris Billings. Palaeozoic Fossils. 1874. v. i, pt 2, p. 40, pi. 



3A, fig. 2, a-c 

 • Eatonia peculiaris Hall & Clarke. Palaeontology of New York. 1894. v. 8, 



pt 2, pi. 61, fig. 17-26 



This is the most abundant of all fossils, in the Grande Greve limestones 

 on the Forillon. Nearly all the fossiliferous layers teem with it and its 

 profusion is in marked contrast to its occurrence elsewhere. In identifying 

 it with the New York Oriskany species to which Conrad gave the above 



