Monthly Microscopican 
Journal, Aug. 1, la&.K J 
from the Coal-measures, 
105 
prepared, I have examined a considerable proportion of those of my 
co-workers, but up to the present time neither they nor myself, 
so far as I have been able to ascertain, have seen a jaw with teeth 
resembhng that I propose to describe to your readers. 
The portion of a jaw about to be described is the more interesting 
because I have obtained from the shale which rests upon the Low 
Main coal-seam in Northumberland a mandible which, so far as 
it is exhibited in the matrix, has the appearance of being mamma- 
lian ; and although I have obtained many hundreds of jaws and 
palate teeth, none of the specimens in my possession resemble it. 
I am therefore not willing to rub it down for microscopic ex- 
amination until I have been fortunate enough to obtain another 
specimen, and am glad to have obtained the fossil to be described, 
because, unhke all fish and reptile teeth I have found and mounted, 
it possesses a long root or process by which it is inserted in the 
dentigerous bone. The teeth of fishes are anchylosed to the aveolar 
borders of the jaws ; the teeth of reptiles are introduced thimble- 
like in series in the jaws ; this specimen departs from both modes 
of attachment, and to that extent at least has one of the leading 
characteristics of a mammal tooth. As I do not pretend to the 
possession of an extensive knowledge of comparative anatomy or 
comparative odontology, I take the hberty of asking through your 
pages the opinions of your subscribers who have made comparative 
anatomy a speciality. 
The question is the more interesting, because if this be a 
mammal tooth it is the first that has been discovered in strata so 
low as the Carboniferous, and that has been submitted to microscopic 
examination. 
The length of the tooth is ^^ths of an inch ; it is inserted for 
two-thirds of its length in the jaw. 
Fig. 1 represents the specimen, natural size. 
Fig. 2 illustrates the same fragment magnified ten diameters. 
The wedge-shaped cavity in the centre of the tooth is the pulp cavity; 
it is rounded at the base : the walls of the tooth consist of dense 
dentine, and are covered with a very thin coating of enamel. The 
roots are two in number, and appear to be divided by a space for 
the insertion of the nerves and arteries which supplied the tooth. 
The spaces in the jaw marked x are filled by the black substance 
of the matrix in which the specimen was found, and are probably 
cavities that have previously been occupied by teeth. Fig. 3 a 
represents the apex of the tooth magnified 250 diameters ; the thin 
outer coating is the enamel, the dark inner space is the apex of the 
pulp cavity, the lines radiating from the dark space are the den- 
tinal tubules which do not extend to the covering enamel. Fig. 4 h 
illustrates the right side of the tooth, half way between the aveolar 
margin of the jaw and the apex of the tooth ; it is magnified 250 
