45 



ivorn. On each side of the umbo of the ventral valve there is (in the 

 casts) a short deep fissure from one to three lines in length. 



Width of a large specimen on the hinge line, twenty-four lines ; aver- 

 age width, eighteen lines. The ribs vary slightly in size in different spe- 

 cimens. There are usually five or six in the width of six lines, next to 

 the fold or sinus. The mesial fold and sinus are from four to six lines 

 wide at the front margin. The fold is often elevated six lines at the 

 front. 



Locality and Formation. — Gasp^ sandstone, Gaspe Bay; in great 

 abundance ; more rarely at Split Rock, Perce. 



Collectors.— W. E. Logan, Dr. J. W, Dawson, R. Bell. 



Spirifera Superba. (N. sp.) 



Plate 3 A, figs. 3, Za, 3b. 



Description. — Shell above the medium size ; with an extremely and 

 angularly elevated dorsal valve, and a very large mesial sinus in the 

 ventral valve. Hinge-line equal to, or a little less than the greatest width 

 of the shell. Sides rounded in the large specimens ; straight in the upper 

 half and rounded below in the smaller. Front margin broadly rounded, 

 or with a portion in the middle either sinuated or projecting, — the outline 

 varying according to the position in which the specimen is viewed _ 

 Width from 2 to 2^ inches. Length varying f rom five-eighths to six- 

 eighths of the length. Depth of both valves sometimes greater than the 

 length. Ventral valve moderately convex, most prominent a little below 

 the hinge-line ; on each side of the umbo abruptly curved down to the edge 

 of the area ; cardinal angles inflected towards the dorsal valve ; umbo 

 of moderate size ; beak small, short, closely incurved over the edge of the 

 area, nearly in contact with the opposite valve ; area about two lines 

 high beneath the beak, concave, forming, in a general way, an angle of 

 about 45? to the longitudinal plane of the shell; foramen rather broad, 

 its sides meeting at an angle of about 90? beneath the beak ; deltidium 

 obtusely angular along the middle, sloping to the sides, only about 

 half closing the foramen, there being a triangular opening between it and 

 the hinge4ine ; mesial sinus inconspicuous on the umbo, but in proceed 

 ing towards the front, rapidly enlarges and greatly elevates the margin of 

 the dorsal valve. It is concave in the bottom, and its sides slope upwards 

 and outwards, gently curving over to the most prominent part of the sur- 

 face on each side. Its greatest width is about two-thirds the whole 

 width of the shell. The curve of the shell along the bottom of the 

 sinus is gentle and gradual fion the front until near the umbo. 



