32 MR. A. L. ADAMS ON THE OSTEOLOGY OF 
reflections with a field of dentine in front ; perhaps a fragment of the preceeding molar 
may have been in use at the same time. The anterior fang has been broken off or is 
worn out, and has left no indications of its presence on the lower surface of the crown ; 
it is difficult therefore even to surmise what may have been the original length and 
ridge-formula of this tooth. But supposing Dr. Falconer’s estimate of the above ' 
correct, this specimen, provided it held fourteen ridges, would have been originally 
about the same dimensions. They agree moreover in their characters; but figs. 
1 & 2 are narrow-crowned as compared with the Zebbug teeth; yet the same 
thick plates, thick enamel, central expansion, abrupt angulations without even faint 
crimping, are common to all. Indeed, as regards the thickness of the enamel, it may 
be stated that the average of the larger plates in the Zebbug (fig. 11) and the above is 
0:5 inch, which is excessive as compared with the lower molar of B series. 
2. The fragment No. 15 (PI. II. figs. 10 and 10 a) shows what appears to me to be 
a left lower molar commencing wear. It is displayed chiefly with the view of 
indicating the outline of the crown in front, thickness of ridges, and the fore fang, 
which is here quite traceable and gives support to two plates besides a diminutive 
anterior talon. All these molars show considerable arcuation of the crowns—more, 
however, in the above and the Zebbug specimens than in PI. IX. figs. 1 & 2. 
It is apparent therefore that there is no evidence whereby the precise ridge-formulas 
of these teeth can be ascertained. Dr. Falconer, reasoning from analogy, as in the 
upper molar® just referred to, gave the lower molar fourteen ridges. And I think his 
hypothesis is now much strengthened if we allow the members of this series to be only 
thick-plated varieties of A series; and considering what has been already shown, and 
what will be further displayed in the next series, it seems to me a fair deduction that 
the above are only varieties of the same molar represented by the entire thin-plated 
tooth, Pl. VI. figs. 1 & 1 a, where we have fourteen ridges, 
C Series.—1. The reclinate condition of the last ridges, pointed out in Pl. VI. fig. 1, 
is repeated in the thick-plated molars 43 A & B (right and left), the former of which is 
represented in Pl. VIII. fig. 9. It is one of a pair found im situ. The left is much 
injured; but fig. 9 is fairly entire, having lost recently a few of its anterior ridges 
supported by the long front double fang. The fan-shaped expansion of the last five 
ridges prolongs the length beyond what would have obtained had they been erect. 
Allowing -for the loss of the three ridges ordinarily borne on the anterior fang, we may 
fairly surmise that this tooth held originally fourteen ridges in a space of certainly 
7 inches, The graduation of the posterior ridges must always add to the length of 
a tooth. 
The disks here, as usual, show the central expansion, with angulations and faint 
crimping ; and, as compared with B series, this may be also called a thick-plated molar ; 
? Zool. Trans. vol. vi. pl. liii. fig. 11. 
* Pal. Mem, vol, ii. pl. xi. fig. 1, 
