408 University of California Publications in Geology [Vol. 12 



A worn upper first molar from the left side (no. 23504, fig. 162) 

 shows the anterior lobe greatly worn, the surface appearing as one 

 large oval tract, though the shape of the outer half of the middle lobe 

 .suggests the trilobed pattern of the inner half. 



A lower molar from the left side (no. 23502, fig. 165) is narrower 

 transversely and tends to be longer anteroposteriorly than the upper 

 molars of intermediate size mentioned above. It is three-lobed like 

 the upper teeth, and of a similar but reversed pattern. The specimen 

 appears slightly more worn than the upper tooth (no. 23503, fig. 164). 

 The outer portions of the anterior two lobes are broken. 



Specimen no. 23505 consists of the two anterior lobes of a greatly 

 worn upper molar (fig. 161). The upper portions of the main lobes 

 have been entirely ground away, the triturating surface on the exterior 

 side being within 9 mm. of the root. The tooth pattern of a less worn 

 stage is replaced by large, hollow, oval-shaped tracts of dentine, 

 embraced by the enamel of the floors of the former transverse valleys. 



A premolar (no. 23506, fig. 163) of very small size, is two-lobed, 

 tliree-fanged, and much worn, little of the original pattern remaining. 

 It is slightly larger than Professor Leidy's figure of the second upper 

 premolar of Mastodon fioridanus,^^ being of about the size of his 

 accompanying cut of a second upper milk molar of the same species. 



A fragment of a premaxilla containing portions of two tusks'^^ is 

 represented in plate 50. The specimens are of oval section, being 

 composed of a central core surrounded by four concentric rings. The 

 surface where unbroken is highly polished; a broad band of enamel 

 is present on each ; the inner texture is striated in the direction of 

 the tusk curvature, which is distinctly inward and outward. 



The collections include an eighteen-inch section of the basal portion 

 of a much larger, but fragmentary tusk, measuring 200 mm. in 

 diameter at the base, and associated with a well preserved pulp core 

 measuring some 600 mm. in length. During the field work still another 

 and larger tusk was uncovered, but disintegration had progressed too 

 far to make the recovery of the specimen practicable. 



Specimen no. 24050 represents the distal portion of a small tusk 

 (fig. 159). The specimen is much flattened transversely, and a trace 

 of enamel having a fine network-like pattern is visible on its basal 

 portion. The tusk is evidently of a young animal. 



56 Leidy, Joseph, and Lucas, Frederic A. Fossil Vertebrates from the Alachua 

 Clays of Florida. Trans. \Vagner Free Inst. Sci., Phila., vol. 4, pi. 4, 1896. 



5" At the time of going to print the basal portions of the tusks have alone been 

 recovered, the upper surface of the adjacent portions lying exposed in the quarry 

 for eighteen inches, and the total length of the tusks being estimated at four feet. 



