372 G. J. HINDE ON ANNELID JAWS FROM 
some Graptolite remains as well as portions of the carapace and 
masticating apparatus of a species of Ceratiocaris. 
The few, but well-preserved, examples of jaws from the Hamilton 
group of the Middle Devonian occur in a very soft mudstone, asso- 
ciated with the spores of Lycopods and Tentaculites. 
In the Lower Carboniferous of Scotland the jaws are imbedded in 
some thin layers of calcareous shale, with Brachiopods and other 
fossils. As, however, there are beds of coal in the section within 
a few feet of this shale, it is not likely to have been laid down in 
deep water. 
It will thus be seen that the strata in which these fossil Annelids 
are present are all more or less shallow-water deposits; and we 
know that similar sandy and muddy beds are the favourite habitats 
of these creatures at the present time. 
Description of the Jaws. 
The Annelid jaws occur as small, dark, shining objects, very varied 
in form, dispersed through the rock, quite detached from each other 
and from the positions they occupied in the head of the animal. 
Occasionally they are met with singly, but more frequently numbers 
of them are associated on the surface of the same slab of rock, and 
sometimes the rock is literally covered with the dark shining frag- 
ments; most of these, on close examination, are thin chitinous par- 
ticles without definite shape, and may have been portions of the 
integument of the animal as well as broken-up fragments of the 
jaws. Except in cases where they have been long exposed to wea- 
thering influences, the jaws are of a bright glossy black tint, not 
showing any difference in those parts which must have been im- 
bedded in muscular tissue, and which in recent examples are gene- 
rally of a lighter horn-colour, whilst the free portions of the jaws of 
the fossil and recent specimens very closely resemble each other in 
appearance. When greatly weathered the black is changed to a 
rusty-reddish tint; but they are capable of resisting atmospheric 
influence to a great degree, and frequently stand out boldly in relief 
on the surface of very hard rock. 
The material of which the jaws are composed appears to be nearly 
entirely of a chitinous character, and so far free from calcareous 
matter that it undergoes no change in nitric acid. 
There is very great variation in the iene ton of the jaws; the 
ereater ahaa os do not average more than 5}, inch in length, but a 
few are 3 inch long and +}; inch wide. In order to form an idea of 
the relative length of worms with similar jaws, I measured the 
principal jaw- Pie in a specimen of the existing Humcea sanguinea, 
whose body was 8 inches long; the jaw-plate was + inch long and 
i. inch wide, If the length of these animals is in proportion to 
that of their j jaws, then the largest of the fossil jaws would belong 
to an Annelid of about 13 inches in length, whilst the ereates part 
would not be more than 3} inches long. 
I may here enumerate the principal forms of the fossil jaw-plates, 
