VERTEBRATES. 157 



and on the other merging into the posterior depression, whose pos- 

 tero-lateral border is broken away, as also the inner and outer por- 

 tions of the tooth. The form was evidently sub-cuneate in ^outline. 

 The coronal surface exhibits the same punctate characters noticed 

 in connection with the terminal form ; however, the transverse undu- 

 lations are less conspicuous. The relative size agrees with the pre- 

 ceding form with which it \yas associated. 



Posterior tooth of the upper jaw elongate triangular in outline, 

 rather strongly arched from within outward, and spirally inrolled. 

 Anterior articular border comprising, perhaps, two-thirds of the great- 

 est length of the tooth from the inrolled outer margin to the very 

 produced inner angle at the base of the principal coronal ridge, 

 gently curved sigmoidally, the narrow enamel fold strongly inbeveled 

 to the deeply-channeled, shallow basal rim; postero-lateral border 

 converging at an angle of 45, more or less, with the anterior artic- 

 ular border gently curved, the thick enamel fold rounded and 

 sharply inbeveled to the correspondingly deep, flaring basal border, 

 from which it is denned by a deep sulcus ; inner margin making a 

 slight angle with the articular border in front, suddenly deflected 

 nearly at right angles in rounding the base of the coronal ridge, and 

 thence passing to the posterior angle with a slight concavity in the 

 region of the posterior depression, worn specimens inbeveled inferi- 

 orly. Principal coronal ridge culminating in a rather sharply rounded 

 crest about one-fourth the distance from the anterior border, pre- 

 senting a steep convexity descending to the shallow depressed belt 

 bordering the articular fold, on the opposite side gently descending 

 into the .wide posterior depression from which abruptly rises the 

 narrow, transversely arched alate expansion, and from which it is 

 defined by a distinct augulation. The coronal surface is more or 

 less regularly undulated transversely, producing a nodose appearance 

 along the crest of the principal ridge. The character of the deli- 

 cately rugose enamel enveloping the inner portion of the crown, and 

 the punctation of the outer worn surface, is precisely as observed in 

 the opposed teeth of the mandible. In both forms, also, the smooth 

 or faintly longitudinally striated inferior surface approximately con- 

 forms to the contour of the coronal region, showing the usual dense 

 thin basal layer. Length of a large tooth along the anterior articu- 

 lar border to inrolled outer margin, 32 mm. or more ; greatest length 

 of tooth along the crest of the coronal ridge, 58 mm. ; breadth be- 

 tween inner angles of the tooth, about 51 mm. ; ditto, between base 

 of coronal ridge and the sub-acute porterior angle, 39 mm. 



