352 THE PALEONTOLOGY OF MINNESOTA. 



lLinj?ula canadensis. 



more obtuse. The ventral valve in L. iowensis and L. beltrami is also less convex 

 than the dorsal, while in L. cincinnatiensis and L. quadrata Eichwald (non Hall) they 

 are equally deep, but the latter is more so than the former. In all of these species 

 there is on the lateral slopes in the anterior half of the interior a more or less con- 

 spicuous wrinkling of the shell which may represent the vascular markings of other 

 species of Lingula. 



Formation and locality. Four specimens have been found by Mr. Ulrich in the Hudson River group 

 between Wykoff and Spring Valley, Minnesota. 



LINGULA CANADENSIS Billings? 



1862. Lingula canadensis BILLINGS. Paleozoic Fossils, vol. i, p. 114, flg. 95. 



1863. Lingula canadensis BILLINGS. Geology Canada, p. 210, flg. 209. 



1889. Lingula? (Lingulasmaf) canadensis ULKICH. American Geologist, vol. iii, p. 384. 



FIG. 26. Copy of Billings' original figure of his Lingula canadensis. 



Original description: "Shell large, oblong, subpentagonal; front margin gently 

 convex or nearly straight; anterior angles narrowly rounded; sides straight and 

 nearly parallel for about two-thirds the whole length, then converging to the beaks; 

 apical angle about 130; cardinal edges ou each side of the beak nearly straight. 

 The valves are moderately convex, most tumid in the upper half, descending to the 

 sides and front margin with three flat slopes. Surface with fine, thread-ljke, elevated, 

 longitudinal ridges, five or six in the width of one line at the front margin; these 

 are crossed by much finer concentric ridges, ten or twelve in one line, which are 

 continued over the longitudinal ridges and give to the surface a minutely nodulose 



appearance." 



The material upon which the above identification is based is rather fragmentary, 

 consisting of two small broken individuals, and a piece of the lateral portion of a 

 large specimen. These are not altogether identical in outline with the figure given 

 by Billings, but since the surface ornamentation of L. canadensis is like that of the 

 Minnesota specimens it has seemed best to refer them provisionally to this species 



