288 PKOCEEDINGS OP THE GEOLOGICAL SOCIETY. 



of the lower jaw, containing the last milk-molar worn low, and the 

 antepenultimate true molar nearly intact. Like the specimen 

 described, the crown is composed of eight principal ridges, with talons. 

 The anterior talon and three front ridges are a little worn, the 

 others entire. The specimen is red and ferruginous, like molars 

 from the " Crag." The dimensions are — 



Inches. 



Length of crown 6*4 



Width of ditto at first ridge 2-4 



Height of fifth ridge 4-0 



The penultimate or second true molar (fifth in antero-posterior 

 succession, and third of the " intermediate" molars) of the lower jaw, 

 is well shown hj a detached tooth of the left side, the crown and 

 fangs of which are complete. It presents nine principal ridges, fol- 

 lowed by a smaller tenth, and a talon-splent behind, so that it is 

 open to regard it as having nine main ridges, with a front and 

 complicated rear talon, or as having ten with a small talon. All 

 the ridges are more or less worn. The tooth, in all its leading cha- 

 I'acters, so closely resembles the others already described, except in 

 the implied condition of larger size, that it is unnecessaiy to de- 

 scribe the crown in detail. The wide separation of the ridges, 

 ample width of the disks of wear, thickness of the enamel plates, 

 and their freedom from plication, are exactly as in the other teeth. 

 In the central disks there is a tendency to an annular expansion or 

 loop, which is directed backwards. In this specimen, also, the two 

 first ridges are supported on a single fang, and the posterior ridges 

 on a shell of confluent fangs. The dimensions are — • 



Inches. 



Length of crown 7"8 



Width of ditto in front 2-2 



Width of ditto at the seventh ridge .... 3-3 



The .same tooth is presented in numerous fragments of the lower 

 jaw, but, in most instances, more or less mutilated or worn out, so 

 as to be less adapted for a distinctive description in reference to the 

 ridge-formula. 



Of the third or last lower true molar detached specimens are 

 numerous in the Florentine Museum, besides a quantity of lower 

 jaws containing it in sitti. 



One mutilated mandibular fragment of the left ramus contains 

 the entire tooth, but not of the largest size, and probably of a 

 female. The crown presents thirteen ridges, with a talon in front 

 and a small talon behind. Of these, the anterior ten ridges are 

 more or less worn — the first three into continuous ; the fourth, fifth, 

 and sixth show a tendency to annular expansion (an outlying den- 

 ticle) in the middle, the loop of enamel being invariably appended 

 to the posterior plate of enamel. The seventh, eighth, and ninth 

 ridges have each about six distinct roundish disks, indicating the 

 same number of massive digitations, with very thick enamel. The 

 tooth contracts very much behind. In all respects the disks of wear 



