47 



front of the umbones also nearly straight or gently concave, the umbonial 

 angle about 135° ; posterior extremity broader thj^i the anterior, gently 

 rounded, nearly at right angles with the dorsal ; ventral margin nearly 

 straight for three-fourths the whole length, narrowly curved upwards at 

 each extremity. Anterior margin consisting of the portion of the dorsal 

 margin in front of the umbones above mentioned. From the umbones a 

 prominent broad gibbosity extends obliquely downwards to the lower pos- 

 terior angle, between this gibbosity and the posterior dorsal angle a gentle 

 slope becoming perceptibly concave on approaching the angle. Surface 

 nearly smooth. 



Width of dorsal margin, from umbones to posterior dorsal angle, 2 lines; 

 from mnbones to anterior ventral angle, li lines ; length of ventral margin, 

 3 luies ; of posterior margin, 2f lines ; depth of both valves, 2 lines. 



Locality and Formation, — Paquette Rapids, on the River Ottawa. 

 Black River limestone. 



Collector. — Sir W. E. Logan. 



LiNGULA PrOGNE. (N. Sp.) 



Fig. 50. Fig. 51. 



Fig. 50. — Lingula Progne. a, dorsal valve ; b, ventral valve. 

 51. — L. Kingstonensis. a, dorsal valve ; b, ventral valve. 



Description. — Shell oblong-oval ; both valves gently and uniformly con- 

 vex ; front margin broadly rounded or somewhat straight ; anterior angles 

 rounded ; sides and the anterior two thirds of the length with the exception 

 of the anterior angles straight or gently convex, parallel ; in the posterior 

 third converging with a slightly convex slope to beaks. The ventral valve 

 is somewhat pointed at the beak with an apical angle of about 70° ; the 

 apex of the dorsal valve is obtusely rounded. Surface with concentric 

 undulations, more numerous in some specimens than in others. In addition 

 to these there are fine concentric striae and longitudinal radiating lines, 

 the latter not visible at all on some of the specimens mitil the surface is 

 partially exfoliated. Colour black, shining. 



Length 5 or 6 lines ; width about f of the length. A specimen found 

 at Montreal 9J lines in length and 5 lines in width appears to belong to 

 this species. 



