VERTEBRATES. 403 



however, recalls the simple coronal fold characteristic of Desmiodus, 

 but there is no indication of the strong anterior buttress and basal pro- 

 tuberance, while the very compressed crown and its sharp denticulations 

 still farther contrast with the latter genus. The character of the basal 

 borders, also, bear some resemblance to Harpacodus, Agass. In view 

 of its minute size, could we detect a horny structure in the place of the 

 apparently true dentine of the tooth, it might be suspected to belong 

 to those curious little fossils known under the general term Conodonts. 



Position and locality : In the lower fish-bed of the Kiuderhook ; Bur- 

 lington, Iowa. 



Ge^tts CALOPODUS, St. J. and W. 



Teeth in general form like Petalodits. Crown massive concavo-convex, 

 concave face deepest, and especially distinguished by its laterally arched 

 or swollen contour, obtuse crest terminating in a strong, subcorneal, 

 more or less eccentric apex; convex face broadly rounded laterally, and 

 more or less arched vertically ; coronal margins more or less prominent, 

 beveled to the base, and occupied by a broad basal band composed of 

 more or less regular or interrupted imbrications, broadest in the concave 

 face and continuous with that of the convex face. Base very similar to 

 that of Petalodus, strong, more or less compressed and constricted above, 

 inferiorly rounded and beveled to an obtuse edge beneath the concave 

 coronal region. 



A single species of the above genus is known to us, which was derived 

 from the Middle Coal Measures. Allied to Petalodus, it may be distin- 

 guished by the turgid, subconical, unsymmetrical crown. The strata 

 whence the following species was obtained, though carefully searched, 

 afford no examples of Petalodus, the non-occurrence of which further 

 renders it improbable that these teeth formed a part of the dental appa- 

 ratus of that genus. 



Calopodtjs apicaus, St. J. and W. 



PI. XH, Fig. 16, 17. 



Teeth very small, robust, unsymmetrical, variable in form. Crown 

 forming a stout, subconical or inequally compressed prominence, crest 

 obtuse, apical extremity eccentric, subacute, directed over the concave 

 face and sometimes laterally deflected; concave face curvilinear or 

 irregularly triangular in outline, lateral diameter nearly equal to the 

 hight, slightly concave vertically, gently arched laterally, basal border 

 moderately and more or less irregularly arched downward, with four or 



