148 



bases of the plates remain at the posterior part of the crown. The 

 remains of the crown are supported by a long, broad, compressed, slightly 

 curved fang, which is solid to near its apex. 



In the Mammoth's grinder the clefts that separate the plates are deeper 

 at the sides than at the middle of the notch, hence the ridges of enamel 

 in a much-worn molar are confined to the outer and inner side of the 

 grinding surface, which is traversed along the middle by a continuous 

 tract of dentine. The outer layer of enamel which covers the dentine 

 below the origin of the plates or transverse lamellar processes is reflected 

 back from the supporting median base of the dentine upon the opposite 

 side of the lateral cleft, bends round the outer margin of the remaining 

 base of the plate, and is continued into the next fissure, and so on. 

 When the ridge of this sinuous coat of enamel is exposed by friction as 

 in the present specimen, it describes a continuous undulating line. 



Mr. Parkinson, who has figured the grinding surface of both this* and 

 the preceding specimen -f~, observes with regard to the latter, No. 612, 

 " The surface of this specimen varies considerably from the recent as well 

 as from the common fossil teeth, in the form and arrangement of its 

 plates. This tooth, which I purchased at the sale of Rackstraw's 

 Museum, was described in the Catalogue as having been taken up with 

 ballast from the bottom of the Thames. 



" Of the variation which takes place in the form and arrangement of 

 the plates in this tooth, it is very difficult to give a description. In the 

 recent teeth, and in the common fossil teeth, the plates are continued 

 straight across the tooth, the enamel being disposed in a long elliptical 

 line, in which the osseous part of the ivory is included. Hence by the 

 abstraction of the surrounding crusta petrosa, as we. have already seen 

 frequently is the case with the fossil teeth, the tooth falls to pieces, and 

 each flat plate is found separated. But in the specimen which has been 

 just examined, an irregularity may be observed in the third anterior row 

 of the plates, where the two digitated processes of a plate passing over 

 little more than half the width of the tooth, are interposed between the 

 second and fourth plate, and thrust a portion of the latter plate rather 

 * Organic Remains, vol. iii. pi. xx. fig. vii. f lb. pi. xx. fig. v. 



