VERTEBRATES. 263 



individuals from either of the forms mentioned, would also seem to 

 indicate their distinct specific character. 



In this connection, it is interesting to note the absence of C. Sjpringeri 

 in the ichthyic bed which affords the form described under the name 

 C.WacJismuthi ; or, in other words, the stratigraphic limitation of each 

 respective form with which that under consideration in one or other way 

 is intimately allied, while the- normal examples of each form present at 

 a glance appreciable peculiarities. 



Geoloyical position and locality : Not uncommon in fish -bed No. 1 of 

 the Kinderhook division of the Lower Carboniferous; Burlington, Iowa 



Cladodtjs Wachsmuthi, St. J. and W. 



PI. 3, Fig 1-7. 



This species presents considerable variation, not only in the teeth from 

 different parts of the jaws, but also in the various sizes, with, however, a 

 well-defined normal standard, which may be defined as follows : Base 

 thick, moderately expanded behind and broadly arched, with a more or 

 less strong sinuous curvature along the outer margin, and nicely rounded 

 at the lateral angles; in front the base is distinctly constricted along 

 the line of union with the crown, expanding outward in its descent, and 

 terminating in a rather strong marginal belt, which generally stretches 

 across two-thirds or more of the median region, and more or less 

 abruptly terminated laterally ; the inferior surface of this belt or ridge 

 is, when well preserved, flattened and beveled inward, and in rare 

 instances it is observed to be more or less distinctly bilobed, iu which 

 cases the belt is relatively of narrower lateral extent, but never cut 

 down so as to break the continuity of the ridge viewed from the outer 

 side ; the inferior surface has its greatest depression immediately below 

 the anterior border, and is usually distinctly beveled along the inner 

 margin; superior surface distinctly defined from the coronal region, 

 moderately convex, and surmounted by a continuous, narrow, pad-like 

 prominence, which occupies half or two-thirds the lateral diameter of 

 the base, and abruptly sloping to the posterior margin ; sometimes the 

 surface immediately above the pad is deeply excavated, and the pos- 

 terior margin somewhat distinctly channeled ; but in the majority of 

 teeth, perhaps, the pad presents a gently rounded prominence, and in 

 worn specimens it may be obsolete ; both basal surfaces are irregularly 

 corrugated antero-posteriorly and pitted by irregularly disposed fora- 

 mina. Crown sharply defined in front and laterally from the base, 

 and a faint line sweeping around the median cone and contracting in 

 the lateral portions, indicating the basal termination of the enamel 

 behind. The central and external cusps are connected by a sharp, 



