NO. 2113. EXTINCT 8IRENIAN DE8M0STYLVS HESPERUS— HAY. 393 



what. There appear to have been present only five columns, two 

 large ones in front, then two smaller ones in a transverse row, then 

 behind and between these another. It is, however, possible that there 

 was a column in front of and between the two first mentioned. No 

 tooth of those described and figured by Yoshiwara and Iwasaki has 

 the structure of this tooth. The corresponding one of their specimen 

 had three columns in the first transverse row, two columns in each of 

 two succeeding transverse rows, and in the rear a single column. 

 This tooth had a length of 64 mm. and a width of 40 mm. Measured 

 where longest the tooth, according to the authors' figure, had a 

 length of 70 mm. 



In the figure of the Japanese specimen there is represented, in the 

 rear of a large bony capsule, portions of three columns of an imper- 

 fectly developed tooth which the authors regarded as the second 

 molar. It is evident that this coiTesponds to the tooth just at the 

 point of eruption in the Oregon skuU. 



In the latter there were seen originally only the summits of four 

 columns; in front a transverse row of two columns, a second row of 

 two columns, and a single column behind aU. Thinking that other 

 columns might be concealed within the jaw, the writer proceeded to dig 

 away a part of the base of the first molar, some bone, and the hard 

 matrix within the cavity. As a result, three more columns were dis- 

 covered in a transverse anterior row, making in all eight (pi. 57- 23). 

 Therefore this second molar agrees in structure with the first upper 

 molar of the Japanese specimen. In the skull before me the summits 

 of the median and inner of the three columns lean rather strongly back- 

 ward. The outer column is considerably shortei' than the others. 

 These anterior columns are lodged partly above the rear of the crown 

 of the first molar. The column which is extruded the farthest is the 

 imier one of the second row. It has a diameter of 13 mm. a short 

 distance above its summit. The unworn summits of all the columns 

 show a thick ring of enamel and in the center of the pit a little eleva- 

 tion. 



Whether or not a third molar might at a later time have been de- 

 veloped behind the one just appearing it is impossible to speak with 

 certainty. Naturally, our specimen tln'ows no light on the lower 

 teeth. In the lower jaw of the Japanese specimen Yoshiwara and 

 Iwasaki found two premolars and a molar. The premolars they, as 

 in the upper jaw, called the first and second; but there are the same 

 reasons for giving these a higher number that we have found in the 

 case of the premolars of the upper jaw. The crown of the tooth which 

 they called the first lower premolar had a length of 32 mm., a width 

 of 20 mm., and a height of about 27 mm. It was composed of seven 

 columns rather irregularly arranged. The second premolars had a 



