108 



The Ottawa Naturalist. [Sept. 



Montrealensts, Billings, in the Black River formation at the 

 Hog's Back- and of Ctenodonta (it should be Cyriodona) breviiis- 

 cula Billings; Ctenodonta, sp.; and Modtolopsis parvtuscula 

 Billings- in^he Chazv formation at the Hog's Back. 



Lastly in a paper on the "Fauna of the Chazy limestone, 

 published' in the American Journal of Science for November, 

 1905 Mr Percy E. Ravmond describes 13 species of pelecypoda 

 from' the Chazv of the' State of New York, and Canada. Three 

 of these are from the neighbourhood of Ottawa, viz., Ctenodonta 

 parvidens, from the Hog's Back; and Whitella Canadensis, 

 and Modtolopsis Sowteri, from Aylmer. The types of these 

 three species are in the Yale University Museum at New Haven. 

 Connecticut. For the opportunity of examining these types 

 and those of Clionychia marginalis, Ambonydna {f)curvata, and 

 Modiolopsis jabcejormis, the writer is indebted to Mr. Raymond. 



The pelecvpoda that are described or referred to on the 

 following pages, were collected by Mr. Walter R. Billings from 

 the Chazv sandstone and shale on the east side of the rapids 

 at the Hog's Back, in the township of Gloucester and county of 

 Carleton, principally in the years 1906 and 1907. They are 

 all mere casts of the interior of the shell, which rarely show 

 any clear indications of the hinge dentition, or well defined 

 imprints of the muscular scars. _ 



From the sandstone which,- Mr. Billings says, immediately 

 underlies the Birds eve limestone at this locality, there appear 

 to be about eight species of pelecvpoda in the collection, though 

 two of them are too imperfect for identification or description. 

 These pelecypoda are associated with Ungida Lyelli, Billmgs, a 

 Holopea, and casts of the interior of the shell of a species of 



Spyroceras. . ^ , ,i • .i 



From the immediately underlying shale there are.m the 

 collection specimens of Ctenodonta parvidens, Raymond, that 

 show imprints of some of the hinge teeth, and several casts that 

 may also be referable to that species, but which show no traces 

 of such imprints. These are associated with Ltngula Belli, 



Billings. . , . . , ,• 11 a.- 



The species of pelecvpoda m this interesting collection 



may be provisionally described or determined as follows:— 

 A. From the Chazy sandstone at the Hog's Back. 

 Clionychia Ottawaensis, sp. nov. 

 Plate III, fig. 4. 

 Shell as indicated bv casts of the interior of single valves, 

 small strongly convex in the median region longitudinally; 

 narrowly, obliquely and acuminately subovate, or mytiloid. 



