139 



0. tricenaria and has the foramen partly closed. 0. disparalis has a 

 more erect beak. I think them all one species ; but as others would not, 

 and as this name has got into use, I shall retain it for the present. 



Locality and Formation. Junction Cliff, Anticosti. In Division 1, 

 Anticosti group ; Middle Silurian. 



Collector. J. Richardson. 



ORTHIS MEROPE. (N. sp.) 





Fig. 116. 

 Fig. 116. Orthis Merope. a, ventral view ; &, area ; c, side view. 



Description. Shell small ; width at the hinge-line twice the length ; 

 cardinal angles acute, from 60 to 70 ; sides and front margin forming a 

 regular semielliptical curve. Ventral valve pyramidal, most elevated at 

 the beak, thence sloping nearly uniformly in all directions to the sides and 

 margin ; area large, at right angles to the plane of the margin, sometimes 

 inclining slightly forward or backward ; foramen large, extending to the 

 beak. Dorsal valve nearly flat, with an obscure mesial sinus. Surface 

 with from 25 to 30 strong, angular undivided ribs. 



Width 3 lines ; length 1J lines. 



Locality and Formation. City of Ottawa. In the lowest beds of the 

 Trenton limestone. 



Collector. E. Billings. 



Genus PORAMBONITES. (Pander.) 



The following species is placed in the genus Porambonites provisionally. 

 Its internal characters are very similar to those of Rhynchonella, but ex- 

 ternally it differs in having an open foramen in each valve and the beaks 

 nearly equal. In these two latter characters it agrees with Porambonites, 

 from which again it differs in having the shell ribbed and the surface not 

 pitted. 



A small generic group might be made to include P. Ottawaensis and 

 the two species figured in the Geology of Russia under the names of 

 Spirifer rectus and S. Panderi. 



