VERTEBRATES. 139 



from Pcecilodus St. Ludovici, and the presence of longitudinal folds 

 in the median depression offers a contrast with P. Cestriensis. 



Geological position and locality: Lower Carboniferous limestone 

 strata; vicinity of Santa Fe, New Mexico. 



PCECILODUS CARBONARIUS, St. J. and W. 



PL VIII, Fig. 20-121. 



Teeth of medium or small size, known from the opposed terminal 

 forms of the upper and lower jaws. 



Posterior teeth of the mandibles characterized by the relatively low 

 coronal ridges, the principal ridge situate considerably posterior of 

 a line traversing the middle of the tooth in the direction of inroll- 

 ment, broadly arched transversely along the inner margin but form 

 ing a narrow angularly rounded ridge toward the outer margin ; 

 anterior ridge narrow, sharply rounded along the crest, steeply 

 sloping to the articular border of the antero-lateral side, and nearly 

 equally abruptly inclined behind into the comparatively wide median 

 depression separating it from the principal ridge, and which is tra- 

 versed by a slight longitudinal fold ; posterior depression defined on 

 the one side by the steep slope of the principal ridge, and on the 

 other moderately rising into the comparatively narrow alate expan- 

 sion of the postero-lateral border, which terminates in the moder- 

 ately produced posterior angle ; postero-lateral border nearly vertical 

 or produced slightly outward inferiorly, defined along the upper edge 

 by the narrow inbeveled enamel fold and slightly channeled ; antero- 

 lateral border not well shown in the accessible examples. Breadth 

 of tooth across the inner margin 17 mm. ; length of antero-latera 

 articular edge 4.5 to o mm. ; longitudinal diameter along principal 

 ridge to inrolled outer margin about 13.5 mm. 



Posterior teeth of the maxillaries in general outline elliptical, rather 

 strongly and spirally inrolled, broadly arched outward along the inner 

 margin with a slight concavity in the region of the median coronal 

 depression; postero-lateral border terminating in a sharply rounded 

 angle, thence gently and regularly curved in its rapid convergence 

 toward point of inrollment, the relatively strong enamel fold inbev- 

 eled to the basal rim from which it is defined by a deep narrow 

 groove ; antero-lateral border very oblique outward and forward to 

 the inner margin, and also apparently defined along the upper edge 

 by a narrow inbeveled enamel fold. Coronal contour regularly and 

 rather strongly arched longitudinally, moderately so transversely; 



