296 TRANSACTIONS OF THE [mAR. 15, 



Dactylodus latus, n. sp. 

 PI. XXIII., figs. 1-1 a. 



Teeth broad, relatively light and thin ; crown from one and 

 a-half to two inches broad, one and a-quarter inches high on tlie 

 posterior face, three-quarters of an inch on the anterior ; roots 

 about four in number, relativel}' short, enamel folds of posterior 

 face distinct, forming a broad sinus in the middle and connect- 

 ing with a less distinctly marked but continuous elevated band 

 at the base of the anterior face, which also forms a deep sinus in 

 the middle; anterior face of crown light in color, smooth, gently 

 arched laterally, straight vertically ; posterior face straight later- 

 ally, slightly concave vertically ; superior margin subacute. 



The teeth which form this group are well represented in the 

 accompanying figures. Their most distinctive features are their 

 great relative breadth and lightness, the vertically straight, 

 smooth, light colored anterior lace of crown, the sinuses of the 

 enameled ridges before and behind. In general form and pro- 

 portions they most resemble the tooth (D. lobatus, N. & W.,) 

 described in Vol. II. of the Report of the Geological Survey of 

 Illinois, p. 4T, PI. 3, fig. 7, but they are ver}' much larger and 

 have the sinuses of the enameled bands more pronounced. It is 

 quite possible, however, that they may be only the mature teeth of 

 the same species. The accumulation of more material will alone 

 decide that question. 



Formation and locality, St. Louis limestone, Alton 111., 

 T3'pe specimen in the cabinet of Columbia University. 



Dactylodus rectus, n. sp. 

 PL XXIII., figs. 8, 9. 



Teeth of medium or small size, mostly about one inch in 

 breadth by three-fourths of an inch in height ; crown broad and 

 low, anterior surface nearl}' flat, inclined to the perpendicular at 

 an angle of about 45^, black and highly polished, terminating 

 below in a broad, cupid's-bow, subacute margin without enamel 

 folds ; root relatively short and broad, composed of four to seven 

 rootlets ; posterior face transversely elliptical with acute ends, 

 vertically slightly concave, horizontally nearly straight, enamel 

 folds at base prominent, forming a simple curve without sinus. 



The above description is based upon a number of teeth of 

 nearly the same size and having somewhat special characters in 

 their broad form, flat, highly polished crown without enamel 

 folds on the anterior face. The posterior face is nearly plane, 



