PLATE IV— Coutinaed. 



ScHiZAMBOx (?) rissus, Kiitorga. 



Fifj'. 31. A i.>edinle-valve ; showiiiaf the external c.hai'acter of the aperture. After Kutorg.I, op. cit., pi. 

 vii, tig. 5a'). X 2.5. " 



SCHIZAMBON (?) FISSUS, Vtir. CANADENSIS, Ami. 



Fig-. 32. A brachial valve from which the shell is partially broken ; showing the impression of an internal 

 median septum. All the spines have been i-emoved except those at and near the mai'u-ins. 

 These have been pre.ssed together in one jilane, giving them the appearance of being more 

 closely set than when standing at their normal angle upon the surface. X 2. 



Fig. 83. The pedicle-valve ; showing the external character of the pedicle-passage. X 2. 



Fig. 34. A pedicle-valve from which most of the shell has been broken, giving a ci'oss-section of the 

 sipho near its inner extremity. X 2. 



Fig. 35. A brac;hial \-alve, the correlate of tig. 34. The surface retains most of the shell, but the spines 

 are broken, showing only their bases, except at the margins where a portion of their length is 

 retained. X 2. 



Fig. 36. A jiedicle- valve, so broken as to show the inner edge of the sipho. 



All the above specimens are from the horizon of the Utica slate. Near Gloucester, 

 Ontario. 



SiPHONOTRETA (?) MiNNESOTENSIS, Sp. IIOV. 



Fig. 37. View from the bi'achial side of a specimen retaining the valves in juxtaposition and preservin"- 

 most of the epiilermal layer of the shell The spine-bases about the beak are noticeably large 

 and more closely set than over the rest of the surface, whei'e they occur at considerable dis- 

 tances along the concentric varices. The entire length of the spines is evidently not repre- 

 sented in the fringe about the n)argin. X 2. 



Fig. 38. The opposite valve of the same specimen. The imperfection of the valve in the umbonal region 

 has rendered it impossible to determine with accuracy the genei-ic character of the species. X 2. 

 Trenton Limestone. Minneapolis, Minnesota. • 



