52 



Locality and Formation. Belleville, Trenton limestone. Also Flat 

 Point, Lake St. John, in the same formation. 



Collectors. E. Billings, (Belleville), J. Richardson, (Lake St. John.) 



DISCINA PELOPEA. (N. sp.) 



Fig. 56. 



Description. Upper valve circular, depressed conical. Apex about 

 half the semi-diameter from the posterior margin. Surface with fine con- 

 centric striae when perfect, but when partially exfoliated, smooth and places 

 polished shining. Colour, black ; width, 6 lines. Lower valve unknown. 



This species is about the size and shape of D. lamellosa, (Hall) but 

 has the apex rather nearer the margin. It differs from D. circe in the 

 same character, and also in being smaller and not so strongly striated. 



Locality and Formation. Montreal. Trenton limestone. 



Collector. $x W. E. Logan. 



TREMATIS MONTREALENSIS. (N. sp.) 



Fig. 57. 



Fig. 58. 



Fig. 59. 



Fig. 57. Trematis Montr ealensis. Lower valve, shewing the small penduncular 



notch. 



58. T. Ottawaensis. Upper valve. 

 59 T. Huronensis. a, lower valve ; b, longitudinal section, shewing the 



curvature of both valves ; c, a portion of the surface enlarged. 



Description. Lower valve transversely broad, oval, depressed, convex, 

 nearly flat ; foramen consisting of a very small notch in the posterior mar 

 gin ; surface with a few concentric striae and undulations ; shell, jet black 

 and where not striated, presenting a polished, shining appearance. 



Width of specimen, 7 lines ; length, 5 lines ; height, about 1 line. 



The greatest convexity is at about one-third the diameter from the pos- 

 terior margin. 



Of this species we have only a single valve. The anterior margin, for 

 about half a line in width is abruptly bent down, and it is not certain that 

 this is the result of accident. 



