YEBTEBBATES. 269 



Cladodus gomphoides, St. J. and W. 



PI. 4, Fig. 12-16. 



Teeth robust, low in stature, of medium or large size. Base slightly 

 sinuate in front, anteroinferior angles moderately prominent, and thence 

 broadly rounded to the lateral extremities, which are also rounded or 

 obtusely angular, and broadly rounded behind ; basal ridge well defined 

 at the anteroinferior angles, depressed in the middle and merging into 

 the margin laterally ; inferior surface moderately excavated, defined 

 behind by a rather broad beveled belt parallel with the posterior mar- 

 gin ; postero-superior surface slightly convex, with a more or less 

 distinct continuous or sometimes interrupted and roughened basal ridge 

 occupying the posterior half of the surface and extending about three- 

 fourths the lateral diameter, and rather abruptly beveled to the poste- 

 rior margin. Coronal cusps very strong, proportionately low, thick, 

 rapidly tapering to the obtusely pointed apices, sublenticular in trans- 

 verse section, both faces presenting rather strong, sharp costte which 

 increase mainly by implantation or rarely bifurcating, and slightly more 

 numerous and crowded behind ; median cone very strong, turgid, rarely 

 faintly depressed at base in front, and generally flanked by two pairs 

 of lateral denticles, of which the inner pair is sometimes rudimentary 

 or obsolete, iu other examples they are strongly developed, the exterior 

 pair slightly deflected laterally and recurved : constricted along basal 

 line in front, also well defined from base behind. 



The form here noticed is represented by a few specimens, among whicb 

 there are only three or four perfect teeth. Although individually vary- 

 ing to some extent, their specific identity is quite apparent, and at the 

 same time they seem to be readily distinguishable from other forms 

 associated iu the same deposits. However, in the case of G. bellifer, a 

 form which we have indicated from a few large teeth derived from the 

 same locality, the chief distinctive features in contrast with the present 

 form consists in the more flattened anterior coronal faces and the more 

 strongly anteriorly produced position of the smaller or intermediate 

 pair of lateral denticles. A large suite of specimens might indeed pre- 

 sent a series of individuals which would connect the extremes here indi- 

 cated by supplying the intermediate and at present missing gradations, 

 without which opinion one way or other is mere conjecture. 



Geological position and locality: In the fish-bed of the upper Burling- 

 ton limestone; Buflington creek, Louisa county, Iowa. 



