Further evidence of Endothiodon bathystoma.

  • Seeley, H. G. (Harry Govier), 1839-1909.
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Further evidence of Endothiodon bathystoma. 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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    OF EJfDOTUIOPON HATH YSTOMA. crowns was not shown. Prom the forms of their bases it seemed not improbable that they might resemble the teeth of Placodus. The present specimen has the crowns perfectly preserved. The longest are more than 2-5 centim. high. They are compressed from side to side, of a long lanceolate form, with strong transverse serrations on the anterior and posterior margins. The dentigerous area is obliquely inclined on the Lacertilian plan, and the different groups of teeth, instead of being arranged from the front backward, as in Theriodonts, succeed each other in the opposite or transverse direction. In front and external to the teeth is a con- cave area 2-25 centim. wide anteriorly, limited by the buccal margin of the bone externally, and bordered internally by a short sharp longitudinal ridge, which prolongs the line of the dentigerous area forward. The concave space between these ridges is prolonged backward external to the teeth, becoming narrower. The first or external row of teeth, which may be incisors, are apparently six in number; the crowns are compressed from side to side, rather wider and shorter than in the other parts of the series, The second or premolar series is counted with difficulty, but appears to number 10 teeth. In no case is the summit of the crown preserved, but the anterior teeth have been worn obliquely on the external side by the teeth in the upper jaw. This condition is well shown in three anterior crowns. The third or molar row apparently includes 15 teeth. In this series the serration of the crown is seen. It has been observed in nearly all the crowns, but from the nature of the matrix it becomes removed in process of development. There is no evidence that it extended below the upper half of the crown. There is a fourth row of six teeth developed on the inner anterior border. These teeth descend in position, as do the hinder molars, as they extend back- ward. The two middle series are between and behind the short internal and external series, which converge forward ; it is possible that this anterior inner group may represent a series of canines, more perfectly developed than among lizards. There is remark- ably little variation in the forms and characters of the teeth in the several rows ; so that if the tooth-rows bear the interpretation suggested for them, it must rest upon their grouping, and not upon differentiation. The roots of the teeth are in sockets, embedded deep in the jaw. In no Anomodont or other reptile has a jaw been described which in any way resembles this in form, muscular attachment, position of the articulation, and form and arrangement of the teeth. Fig. 3.—Teeth (enlarged) showing serrations. •§ nat. size.