Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/589

 boscidia indicated in my ' Odontography' as "transitional forms"*, since defined by Falconer under the generic name Stegodon†, of which he gives as one character, " the enamel is very thick, and the coronal interspaces, in most species, are filled up with an enormous quantity of cement"‡ — an admission of exception which significantly points to the difficulty of defining or circumscribing the generic groups in the grand gradational series of modifications of the Proboscidian order, for the knowledge of which science is mainly indebted to Kaup, Clift, and Falconer.

Stegodon orientalis, Ow.

The molar of Stegodon sinensis, above described, alleged to be " from marly beds in the vicinity of Shanghai," showed by its colour and mineralized condition that it had been derived from some such, probably tertiary, deposit.

The portions of proboscidian molars which I have next to notice are in a less altered condition. The dentine retains its original white colour, and has only lost its soluble constituent, which causes it to adhere, like chalk, to the tongue; the enamel also has its recent pearly tint ; a thick mass of cement appears to have been retained in the intervals of the coronal ridges.

One of these ridges, with the contiguous halves of two others, form a molar two inches nine lines in breadth (Pl. XXVIII. figs. 1 & 2) ; a portion of a posterior ridge with a low basal heel, from the same, or the same-sized tooth, and the last two ridges, with a terminal half ridge or talon, of a milk-molar, one inch and a half in breadth (ib. figs. 3 & 4), represent the present specie.

These fragments form part of the series of teeth obtained by Mr. Swinhoe, and said to be "from a cave, near the city of Chung-king- foo, in the province of Sze-chuen." The condition of the fragments agrees with the statement, viz. that they were from a cavern.

In the largest fragment a longitudinal extent of grinding-surface of two inches includes the summits of three ridges. The basal breadth of the ridge (ib. fig. 2) b b is one inch ; its height (unworn) is one inch four lines, measured along the sloping side. One slope, I think the anterior, is rather more inclined than the other. The ridge (ib. fig. 1) a a runs straight, or nearly so, across the tooth ; the entire ridge is cleft at the summit into about a dozen mamillae by as many vertical grooves ; the dentine rises into the base of each mamilla. The enamel (e) averages two lines in thickness.

From the above-defined characters it is plain that we have here, also, parts of a " transitional Mastodon," in other words, a species of Stegodon, Fr. In the straight, or nearly straight, direction of the coronal ridges, and the absence of any trace of mid cleft, these molar fragments more resemble the teeth of Stegodon Cliftii, St. insignis, and St. ganesa of Falconer than does the St. sinensis; and


 * ' Odontography,' Proboscidia, Section 228.

† "Elephas we divide into three sectional groups, viz. Stegodon, being the species which Owen calls Transitional Mastodons, the M. elephantoides of Clift, and of which there are three, and perhaps four, Indian fossil species." — Palaeontol. Memoirs, vol. i. p. 20.

‡ Palaeontological Memoirs, vol. ii. p. 9.