FROM THE CARBONITFEROUS LIMESTONE OF ILLINOIS AND MISSOURI. 89 
CHOMATODUS, AG. 
5. CuomATopuUS VENustuS, Leidy. 
This species is founded on the specimen of a tooth, the crown of which forms a narrow, 
oblong, quadrilateral plate elevated on the outer side, into an obtuse ridge. The latter 
rises towards its middle into a mammillary eminence with a truncated apex, centrally im- 
pressed and punctured at the margin. Along the summit of the ridge, to one side of the 
principal eminence, there are five other similar but comparatively minute ones, and on the 
opposite side there are several others nearly obsolete. The internal side of the crown is 
depressed, and is bordered by four or five delicate folds of ganoine, which are likewise in 
a much enfeebled condition, extended on the outer side of the crown. The root of the tooth 
is a narrow, thin, flat plate extending in the direction of the crown. Length of the spe- 
cimen seven lines; breadth at middle two lines; depth at middle one and a half lines. 
Locality —F rom the Carboniferous limestone of Warsaw, Hlinois. Plate V. Fig. 19. Tri- 
turating surface of the tooth of Chomatodus venustus, magnified three diameters. Fig. 20. 
Profile section of the same tooth at the middle; three diameters. Fig. 21. Profile section 
at one side. 
6. CHOMATODUS oBscuRUS, Leidy. 
This species is proposed on a fragment of a tooth, the crown of which in its perfect con- 
dition appears to have been an oblique, oblong, quadrilateral plate, with an obtuse, com- 
pressed hemi-elliptical ridge extending along the outer part of the triturating surface. 
The latter is bordered by a basal ridge apparently worn smocth in the specimen, except 
in one position, where it exhibits five folds of ganome. The root is hemi-elliptical, ex- 
tended in the length of the crown, and is twice the depth externally that it is internally. 
Height of the specimen four and a quarter lines; antero-posterior diameter of the crown, 
when perfect, about four and a quarter lines; probable transverse diameter twice its pre- ~ 
sent extent, which is seven lines; depth of root internally two lines, externally four lines. 
Locality.—The Carboniferous limestone of Warsaw, Illmois. Plate V. Fig. 22. Tri- 
turating surface of the tooth of Chomatodus obscurus. Fig. 25. Profile section of the tooth. 
PALAEOBATIS, Leidy. 
7. PALAEOBATIS INSIGNIS, Leidy. 
This species is proposed on a fragment of a remarkable tooth, recalling to mind one of 
the dental plates of Myliobates, of which plates the specimen apparently corresponds to 
the half of one. The upper surface of the crown is a linear plane, and its posterior side | 
presents a single row of deep pits, of which about four may be counted in each line of ex- 
tent; and below the row of pits a band-like basal ridge without folds, separates the crown, 
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