Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/587

 one may make out in the reduced figure (half natural size) the presence, but not the number, of marginal mamillae on the fourth or penultimate ridge. But whilst this figure illustrates the degree of correspondence, it serves at the same time to show the specific degree of difference between the second upper milk-molar of Mastodon (Stegodon) sinensis and Mastodon elephantoides, Clt., or Stegodon insignis, Fr.

The original of Falconer's figure being in the British Museum, yields the following admeasurements, giving the difference in size and proportions between : —

Steg. sinensis. Steg. insignis. in. lines. in. lines. Length of crown 2 10 2 6 Greatest breadth of crown 2 0 2 1-1/2

In Stegodon sinensis the deciduous tooth is longer (antero-posteriorly) in proportion to its breadth. The tubercle at the outer interspace between the first and second ridges is larger and situated more immediately upon the interspace, closing it externally. The transverse divisions increase in breadth from the first to the fourth, the last being narrower, though not to the same degree as in Steg. insignis; neither do the ridges increase so regularly to the fourth in the Ava and Siwalik species as in Steg. sinensis. The ridges in Steg. insignis are loftier as well as narrower than in Steg. sinensis ; the sculpturing is somewhat coarser ; the fourth unworn ridge shows about twelve mamillae. The fangs or roots of the tooth are not defined in the Siwalik tooth. In the Chinese one the fore part of the crown, divided externally into the two anterior ridges (Pl. I. fig. 2, 1 & 2), is supported by one fang deeply grooved on the side turned toward the second : this root is much larger, and supports all the remainder of the tooth ; its base being entire, we are able to infer that only the hind part of the last coronal ridge (5) has been broken away, and that there could not be any added talon at that end of the tooth. The anterior vertical surface of the crown (ib. fig. A) shows a smooth concavity with the enamel worn through to the dentine by the pressure against the antecedent molar (d 2). The thick layer of cement which coats the dentine of the base of the tooth and its two divisions is well preserved, which leads me to doubt whether it could at any time have existed in the coronal clefts of the teeth of the present species.

The molars of Elephas (Stegodon) insignis, Fr., chiefly differ from those of E. (St.) Cliftii, Fr., in the much greater mass of laminate cement that fills up the valleys*. As this difference is to be added to those above described, it further opposes the reference of the Chinese proboscidian tooth to the St. insignis.

Of the Elephas (Stegodon) Cliftii, Fr., no tooth has yet been acquired homologous with the Chinese specimen. From the general analogy of retention of pattern of grinding-surface, notwithstanding the increase of size and number of coronal ridges as the molars recede in position, we may certainly infer, from there being no mark


 * Falconer, ' Palaeontological Memoirs,' 8vo, vol. ii. p. 85.