164 ^Ir. T. Atthey ou Anthracosaurus Russelli. 



cavity ; the offsets from this arc the pulp-cavities of the tooth- 

 lets ; the part between the extremity of the offset and the 

 exterior of the tooth, consisting of radiating tubules and im- 

 bedding 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 toothlets, or their line of union, accord- 

 ing 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 plicje are much less 

 tortuous 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 plica3 or elsewhere. No cementura is any- 

 where visible. 



In my cabinet, the following separate bones of Anthraco- 

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



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

 surface exposed, and measures 8^ inches in length by 1^ inch 

 in breadth at 3| inches behind its anterior end ; from this 

 point it diminishes slightly forwards, but much more rapidly 

 backwards. It bears 19 teeth, all of which are perfect and, 

 with the exception of the last, measure | inch in length from 

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

 their base in the ti-ansverse direction of the jaw, in which they 

 are 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 ~^^ inch behind the fourth, and the like dis- 

 tance in front of the sixth and seventh, which are in contact 

 with each other ; -^ inch separate the seventh from the eighth, 

 which is the same distance in front of the ninth, tenth, eleventh, 

 and twelfth, which are in contact with each other ; after an in- 

 terspace of -^(j inch come the thirteenth and the other six, 

 which are all nearly \ inch apart from each other. Their sur- 

 faces appear to be eroded, which gives to the teeth a ridged 

 appearance. The seventeenth tooth has been extracted ; and 

 the microscopic sections represented on Plate XI. figs. 1, 2, 3, 4 

 were made from it. 



One quadrate-jugal bone, in a good state of preservation, 

 showing both its surfaces. The upper surface shows the deep 

 depression or mucus-groove along its outer margin, as figured 

 in Plate VIII. fiw. 1, also the tubercle with the line from it 



