VEBTEBRATES. 267 



Cladodus intercostattts, St. J. and W. 



PI. 4, Kg. 11. 



Teeth of small or medium size. Base subelliptical iu outline, mode- 

 rately thick, posterior margin broadly rounded, with obtuse angles, 

 extremities more or less sharply rounded, anterior margin sinuose, with 

 a broad mesial depression, slightly produced, anterior angles occupied 

 by well-defined protuberances, which are conuected by a well-marked 

 basal ridge; inferior surface moderately excavated, beveled along the 

 posterior margin, postero-superior surface moderately convex, surmoun- 

 ted near the posterior margin by a laterally elongated, narrow, rough- 

 ened prominence equal to about half the lateral diameter of the base; 

 both superior and inferior surfaces irregularly pitted. Crowii gently 

 constricted in front, obscurely defined behind, median cone symmetrical 

 rapidly tapering to an acute point, gently recurved, sublenticular in 

 transverse section with trenchant edges, broadly arched behind, in front 

 compressed and towards the base slightly excavated, both faces occu- 

 pied by strong, sharp costse, those in the posterior face perceptibly finer 

 and terminating in the lateral margins, in front a strong ridge extends 

 from base to apex parallel with and separated from either border by a 

 rather wide slight depression, the intermediate space being occupied by 

 equally strong bifurcated and implanted cost'se ; lateral denticles two on 

 either extremity, the exterior pair as strong again as the intermediate 

 denticles, strongly deflected laterally or divergent, and recurved at an 

 angle greater than the median cone, subcircular in section with sharp 

 cutting edges, inner pair slightly produced in front, similar in section 

 and ornamentation to the larger denticles, a few strong vertical costse 

 occurring in either face and occupying the low intermediate coronal 

 ridge. A specimen of medium size measures in greatest lateral diame- 

 ter of base .36 inch, antero posterior diameter .12, greatest hight of 

 teeth .29 inch. 



The above description applies to a form not numerously represented 

 iu our collections, and with regard to the affinities of which with other 

 teeth associated with them, there is. matter of some doubt. All the 

 individuals which have been identified with the above form are small, 

 and some of these show indications of a third rudimentary lateral den- 

 ticle, while there are others which possess a fourth pair, but with pre- 

 cisely the same, or even relatively coarser coronal cost®. With these 

 also occur in considerable abundance a larger form, which is character- 

 ized by several lateral denticles, and along the outer coronal margin a 

 greater or less development of spinose processes, while the costaj are 

 relatively fiuer, though similarly disposed, and. the base offers no essen- 



