ME. T. ATTHEY ON ANTHEACOSATJEIJS ETJSSELLI. 329 



are spread out in a fan-like expansion, and, after passing through 

 a series of finely-arched lines crossing them, reach the exterior 

 of the tooth. 



The teeth of Anthracosaurus are, in fact, like those of Lox- 

 omma, formed of a series of toothlets surrounding the pulp- 

 cavity; the offsets from this are the pulp-cavities of the toothlets; 

 the part between the extremity of the offsets and the exterior of 

 the tooth, consisting of radiating tubules and imbedding dentine, 

 forms the crown of the toothlet ; whilst the fangs are formed by 

 the sides of the offset of the pulp-cavity — that is, by one half of 

 a sinuous tract of light dentine, the narrow, dark, granular, 

 infolded band indicating the line of separation between the tooth- 

 lets, or their line of union, according to the view taken of the 

 matter. 



Of these toothlets there are about twenty-four, large and 

 small, together ; and their crowns form the ridges seen on the 

 exterior of a tooth. 



In Loxomma the dentinal tracts or plicae are much less tor- 

 tuous than the corresponding parts in Anthracosaurus ; but the 

 infolded band, which is dark in the latter, is light in the former. 



The arrangement of a compound tooth is really the same in 

 both these animals. Enamel is visible ; but certainly none is 

 infolded into the plicae or elsewhere. ~No cementum is anywhere 

 visible. 



In my cabinet, the following separate bones of Anthracosaurus 

 from our coal-shale, and not already noticed, occur : — 



One right maxilla. — This lies in the matrix with its inner 

 surface exposed, and measures eight inches and a half in length 

 by one inch and a quarter in breadth at three inches and a half 

 behind its anterior end; from this point it diminishes slightly 

 forwards, but much more rapidly backwards. It bears nineteen 

 teeth, all of which are perfect, and, with the exception of the 

 last, measure three-quarters of an inch in length from the base 

 at the alveolar border to the apex. They are oval at their base in 

 the transverse direction of the jaw, in which they arc arranged 

 as follows : — The first four are placed at a short distance behind 

 the anterior end, and are in contact with each other ; the fifth is 



