On the Gomphodontia / by H.G. Seeley.

  • Seeley, H. G. (Harry Govier), 1839-1909.
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: On the Gomphodontia / by H.G. Seeley. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    the length which is occupied by the molar teeth. The lateral contours of the dentary bone are similar to those of other Theriodonts. The basal contour is almost straight to the angle, where the bone recedes at about 45° upward and backward, forming a sharp posterior edge, which is nearly straight, and rests superiorly upon the articular bone, so as to expose the articular condyle in a position which is external to the dentary bone not seen in other specimens. Above the articulation the posterior truncation of the coronoid process of the dentary bone appears to be vertical. The coronoid process is compressed to a knife-like thinness, and its superior border behind the teeth is slightly convex in anterior contour, just as the alveolar margin is slightly concave. The coronoid region may be regarded as prolonged forward by the inflation of the bone below the teeth, which gives a slight convexity to the upper half of the external side of the jaw. The incisor teeth are arranged transversely in a slight crescentic curve. All have lost their crowns, they are six in number, equal to three in each ramus. The transverse measurement over the third pair is inch. The teeth appear to be transversely ovate ; they may decrease slightly in size from the first to the third. Immediately behind the incisors are the longitudinally ovate canine teeth inch long, and inch wide. The crown now broken away, appears to be compressed posteriorly, and directed a little outward as well as upward. The canine teeth are separated from each other by a deep channel which is the beginning of the division between the rami. The crowns are large and longitudinally ovate. Immediately behind the canines is the diastema, rather less than inch long, with a slight sharp median ridge. To this succeeds the molar teeth which occupy a length of inches. They are 13 in number on each side of the jaw. The first three or four are conical, with the crowns enamelled, slightly expanded posteriorly at the base of the enamel, so as to form a posterior cusp, and there is also a slight anterior cusp. The principal cusp is serrated on the posterior border ; but although the anterior margin is compressed and rugose, the serrations appear to take the form of beads, which are broken away. The external surface of the crown is convex ; but the internal surface is concave from above downward, owing to the transverse thickening due to the development of a cusp at the base of the crown on the inner side. This internal heel I regard as the most distinctive character of the teeth in this genus, coupled with the slight indication of the posterior cusp on the external surface. Few of my specimens, however, show the internal aspect of the teeth ; and evidence will hereafter be given that a tooth of not dissimilar type, though wanting the lateral cusp, and having the crown more elevated, characterizes Tapinocephalus. The five succeeding teeth are badly preserved in both rami, and have lost the summit of the crown, but whether this is entirely due to breakage or partly the result of wear is not evident, though there are some indications that the teeth are worn, especially in the condition of the eighth and ninth on the right side. The last four on the right side show indications of the crown. It is convex