VERTEBRATES. Ill 



margin, basal portion channeled and produced downward and out- 

 ward in a thin rim, denned above by the narrow inbeveled enamel 

 fold ; postero-lateral border converging toward point of inrollment 

 somewhat more rapidly than in the case of the opposed mandibular 

 teeth, with which it bears much the same characters in respect to 

 the basal portion and enamel fold along the upper edge ; inner 

 margin most arched round the base of the posterior coronal lobe, in 

 front of which it is more or less deflected inward and forward, 

 thence gently arching round the anterior prominence to the obtuse 

 anterior angle. Coronal region divided into two principal revolving 

 elevations, of which the posterior one is much the most prominent, 

 occupying about half the lateral diameter of the crown, the broader 

 slope rising from the postero-lateral border and culminating nearer 

 the anterior side, with a more abrupt slope descending to the median 

 depression; the latter presents a broad transversely more or less 

 concave area, the surface rising anteriorly into the more or less 

 well-defined anterior prominence, thence the slope descends to the 

 antero-lateral border. The coronal surface is further marked by 

 more or less distinct, though generally obscure and sometimes obso- 

 lete subordinate revolving ridges and furrows which are chiefly 

 noticeable in the region of the anterior prominence, though some- 

 times present in the median depression and the long slope of the 

 posterior prominence ; more or less distinct transverse rugae dis- 

 posed in the same manner noticed in connection with the mandi- 

 bular posterior teeth, occur, producing an elegant imbricated orna- 

 mentation in the individuals thus distinguished. The latter super- 

 ficial feature is, however, obsolete in some species, and which is 

 equally applicable to all the other forms of certain species of un- 

 doubted congeneric relationship. 



In regard to the character of the teeth occupying the extremities 

 of the jaws, we can little more than conjecture their identity. 

 Amongst the numerous examples of transversely elongate teeth 

 which were originally disposed in serial order, and which are recog- 

 nized under various generic appellations which in themselves con- 

 stitute well-defined groups, there are possibly included forms which 

 may have been associated with the teeth under present considera- 

 tion. 



The generic relations of the forms embraced under the above 

 designation are most intimate with Cochliodus, Agass. Indeed they 

 differ chiefly in the less well defined differentiation of the coronal 

 regions, while in Cochliodus these parts are sharply limited, the 



