218 Annals of the Carnegie Museum. 



3. Lingula columba Ra\ niond. 



(Plate XXXIII, figures 3, 4.) 

 Lingula columba Raymond, 1905. American Journal of Science, Series 4, Vol. XX, 

 p. 368. 



Shell small, oval in outline, gently and uniformly convex. The 

 front is semicircular in outline, the posterior end somewhat triangular, 

 the beak pointed. The surface is covered with very numerous and 

 prominent concentric striae, no radiating lines showing, except when 

 the shell is partially exfoliated. 



One specimen is 10 mm. long and 7 mm. wide. Another is 7 mm. 

 long and 5 mm. wide. This species is not so abundant in any place 

 as Lingula brainerdi, but it is more often met with, as it ranges through 

 a much greater thickness of rock, and has about the same geographic 

 distribution. 



Locality. — This species is fairly common in the Chazy limestone 

 at Valcour Island, and Chazy, New York, and at Isle La Motte, Ver- 

 mont. 



4. Lingula lyelli Billings. 



(Plate XXXIII, figures 5, 6.) 

 Lingula Lyelli Billings, 1859. Canadian Naturalist and Geologist, Vol. IV, 



p. 348, figs, la-id; p. 431. 

 Lingula Lyelli Billings, 1863. Geology of Canada, p. 124, fig. 49. 



Lingula lyelli occurs in great abundance in the soft clayey shales of 

 the Aylmer formation in the Ottawa Valley and exhibits a considerable 

 variation in form. Young specimens correspond almost exactly to 

 Billings' descriptions and figures, but some of the adults depart so 

 far from the sub-rectangular form that they more nearly resemble 

 Glossina belli than the normal form of Lingula lyelli. The straight 

 sides and the long slope of the anterior margin are, however, always 

 present. 



Description. 



Outline somewhat oval, pointed posteriorly, and broadest in front. 

 Dorsal valve shorter than the opposite one, the posterior margin 

 rounded instead of triangular. Each valve shows three flat slopes, 

 one on each side, and one extending from near the beak to the anterior 

 margin. The sides of young specimens are straight and nearly 

 parallel. The adult shells are widest toward the front and the sides 

 converge backward. A few specimens show three faint longitudinal 

 folds on the frontal slope of the pedicle valve. The surface is usually 



