170 



and at Little Tamarack Island by D. B. Dowling in 1890; at Clark's or 

 " Limestone " Point, eleven miles north of the mouth of the Little Sas- 

 katchewan, at an exposure eight miles north of Clark's Point, and on the 

 west shore of the lake, north of the Saskatchewan and opposite the 

 north end of Selkirk Island by D. B. Dowling in 1891. Nearly all 

 the specimens from these localities are dorsal valves in various states 

 of preservation. They are here referred to Owen's species, which has 

 not yet been satisfactorily illustrated, mainly on the authority of Mr. 

 Charles Schuchert, to whom three of the best specimens were sent for 

 comparison, and who regards them as "typical examples of Strophomena 

 trilobata, as found in the upper Mississipi valley.'' 



Strophomena. (Species uncertain.) 



A few dorsal valves of a Strophomena, whose specific relations are at 

 present uncertain, were collected at Lower Fort Garry by Dr. Bell in 

 1880 and by Mr. Weston in 1884. So far as can be ascertained from 

 their imperfect state of preservation, these specimens would appear to be 

 intermediate in their characters between S. trilobata and S. Hecuba, 

 Billings.* In the dorsal valve of S. trilobata the visceral disc is flattened 

 and the remainder of the valve bent abruptly inward at an obtuse angle, 

 at about one-third of the length from the beak to the nasute anterior 

 extremity, while that of S. Hecuba is ventricose and evenly convex. 

 These dorsal valves from Lower Fort Garry are tumid and gibbous a 

 little behind the midlength, when viewed laterally, and neither obtusely 

 angulated posteriorly, as in S. trilobata, nor uniformly convex as in S. 

 Hecuba. They may possibly indicate or represent a nasute local variety 

 of ;5^. incurvata. 



Strophomena Billingsii, Winchell and Schuchert. 



Strophomena recta, Billings 1862. Geol. Surv. Canada, Pal. Foss., ^o\. 



I., p. 130, figs. 108, a-c. But apparently not 

 S. recta, Conrad, 1843. 



SiTOpfeomema^iMwijrst, Winchell cSiSchuchert.1893. Lower Silur. Brach. Minn., p. 397, 



figs. 32, a-c. 



East Selkirk, Manitoba, T. C. Weston, 1884 : four specimens, on two 

 small pieces of limestone. 



Rafinesquina deltoidea, Conrad. (Sp.) 



Strophomena deltoidea, Conrad 1839. Third Ann. Rep. Geol. Surv. N.York, 



p. 64. 



I. 1841. Fifth Ann. Rep. Geol. Surv. N.York, 



p. 37. 



* Vide Geological Survey of Canada, Palseozoio Fossils, vol. I., p. 126, fig. 104. 



