VERTEBRATES. 



the inner angle of the coronal ridge to the inrolled outer extremi 

 about 11.5 mm ; greatest breadth across inner margin, 9 mm. 



As yet other forms which were probably associated with the above 

 tooth have not been recognized. Indeed it is only within a recent 

 date that the Warsaw beds have afforded many fish remains, and 

 in most instances these, represent forms peculiar to the formation. 



Geological position and locality: Warsaw shaly limestone, Golden 

 Bluffs, near Warsaw, 111. 



DELTODOPSIS ST. LUDOVICI, St. J. and W. 



PI. XI, Fig. 2-6. 



Mandibular posterior teeth depressed, triangular in general outline, 

 moderately arched longitudinally and inrolled. Autero -lateral border 

 comprising a little more than one-third the extent of the tooth 

 along the coronal ridge, gently curved from within outward, basal 

 rim slightly furrowed and bordered by the distinct, narrow, iubeveled 

 enamel fold ; inner margin in front diverging at a slight angle from 

 the anterior angle to the base of the coronal ridge, round which it 

 is sharply curved with a slightly concave course to the acute pos- 

 terior angle of the alate expansion, inferiorly inbeveled ; postero- 

 lateral border gently arched, gradually converging toward the sud- 

 denly inrolled outer extremity, the narrow inbeveled enamel fold 

 distinctly denned from the nearly vertical channeled basal border. 

 Coronal prominence culminating in an obtusely rounded ridge near 

 the median line, anterior broad slope nearly plane or slightly con- 

 vex, more abruptly sloping into the depression on the opposite 

 side, which is bordered by the moderately upraised narrow alate 

 expansion of the postero-lateral border. Crown surface minutely 

 and somewhat irregularly punctate, unworn surfaces showing 

 numerous delicate transverse furrows parallel with the inner margin 

 and producing a slight undulated appearance; in some examples 

 the exfoliated enamel reveals a surface delicately striated by wavy 

 threads holding the same course as the undulations. A tooth of 

 medium fsize measures along the articular anterior border to 

 point of inrollment 8.5 mm; transverse diameter across inner mar- 

 gin 13.5 mm; length along crest of coronal ridge 19 mm. 



Mandibular median tooth subtrapezoidal in outline, moderately 

 arched longitudinally, outer extremity strongly inrolled spirally for- 

 ward. Postero-lateral border gently curved conforming to the 



