106 The Ottawa Naturalist. [Sept. 



must remain un described until better can be procured." He 

 then proceeds to identify some specimens from the Canadian 

 Chazy with Ctenodonta nasuta (Hall), and to describe three 

 new species, under the names Modiolopsis parviuscula. Cyrto- 

 donta breviuscida, and Vantixemia Montrealensis, but figures 

 only the latter. In regard to these four species the following 

 notes are submitted. 



Ctenodonta nasuta (Hall). 



Mr. Billings says that this species "occurs in the Chazy 

 sandstone at Lac Aurau River above the River Rouge, and 

 also at the Mingan Islands in the Chazy limestone." The 

 writer has not seen any specimens of it from the first of 

 these localities, which should read — at Lac Oureau River, 

 above the Riviere Rouge, in Joliette Co. In the Museum 

 of the Geological Survey there are two casts of the interior 

 of the shell of specimens, labelled "Ctenodonta nasuta 

 (Hall, sp.), Mingan Islands, Logan and Richardson, 1856." 

 These are probably the specimens referred to on page 134 

 of the "Geology of Canada" (1863), which are said to be 

 from the "bay above Clear Water Point," which is on the 

 north shore of the Gulf of St. Lawrence, opposite the 

 Mingan Islands. 



Modiolopsis parviuscula, Billings (PI. Ill, figs, l and 2). 



This species is very inadequately defined, and it has 

 not previously been figured. All that is said of it by Mr. 

 Billings is that it "closely resembles M. modiolaris (Conrad); 

 but is always less than half the size of that species. It 

 occurs in the Chazy limestone at Montreal, near Cornwall, 

 at the Mingan Islands, on the Islands at Lake Huron, and 

 also at Punk Island, Lake Winnipeg." The only authenti- 

 cally named specimens of M. parviuscula that the writer 

 has seen are a single right valve from Cornwall (fig. 1), 

 collected by Mr. Billings; and four badly preserved casts 

 of the interior of single valves from Punk Island, collected 

 by Professor H. Youle Hind in 1858 (one of which is repre- 

 sented bv fig. 2). All of these are in the Museum of the 

 Geological Survey. 



In regard to the comparative size of M. modiolaris 

 and M. parviuscula, the following measurements may be 

 of interest. The maximum length of the largest and most 

 perfect Canadian specimen of M. modiolaris in the Museum 

 of the Geological Survey is 68 mm. (or nearly 2| inches); 

 and that of another, in the same museum, is 61^ mm. (or 



