Raymond : Brachioi'oda and Ostracoda of the Chazv. 237 



sixteen to twcnty-hvc simple, rouiKk-ci plicaliDiis, which increase by 

 implantation. 



Fig. 10. Orlhis ignkula Raymond. Side, dorsal, and cardinal views of a 

 small specimen. One-halt larger than natural size. 



Fig. II. The same species. Dorsal, ventral, and cardinal views of a larger 

 specimen. Same magnification. 



Locality. A rare species, found so far only on X'alcour Island, where 

 it is most commonly associated with Camarotcechia plena at Cystid 

 Point. 



20. Orthis acutiplicata Raymond. 



(Plate XXXV, figures 8-io.) 



Orlhis acutiplicata R.wmond, 1905. American Journal of Science, series 4, Vol. 

 XX, p. 370. 



In the sandy and dolomitic layers near the base of the Chazy at 

 X'alcour Island there is an Orthis which differs from both Orthis ignicida 

 and 0. costalis in having the brachial valve more convex, and in having 

 few'er plications on the surface. It seems to have only a limited vertical 

 range, and has been found at only one locality, where, however, it is 

 quite abundant. 



Description. 



Shell small, almost circular in outline. Width at the hinge not quite 

 equal to the greatest width below. Cardinal area of pedicle valve 

 high, nearly flat. Delthyrium narrow, deltidium not preserved. 

 Brachial valve convex on the umbo, flattened in front. Surface marked 

 by from twelve to fifteen simple plications which are separated by 

 spaces wider than themselves. 



Locality. — Near base of the Chazy at the southern end of \'alcour 

 Island, New York. 



