80 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 
Interiors normal. 
Hinge-line arched, edentulous, surmounted posteriorly by a longitudinal 
hollow groove or elongated escutcheon, below which the ligament arises from a 
faint linear groove on the extreme edge of the shell. 
Dimensions (fig. 29) : 

Antero-posteriorly ; : ; . 25 mm. 
Dorso-ventrally : : : . 6mm: 
Laterally . . : : » L2imm: 
Locality.—Caleiferous Sandstone Series, Kilminning and Kilrenny Mill, Fife ; 
where it occurs at two horizons, one a hard shell bed in large numbers, the 
other a siliceous limestone with Littorina (?) Scotoburdigalensis twigs of 
Lepidodendron. 
Observations.—I am indebted to Mr. Kirkby, of Leven, Fife, for the opportunity 
of studying these shells. They are interesting as occurring very low down in the 
Carboniferous series, and are probably the oldest form of Carbonicola known if I 
am right in my determination. Mr. Kirkby tells me that the late Mr. Salter 
referred them to Anthracosia. In support of this view, the lunule and general shape 
of the shell are very characteristic of Carbonicola, and I can discover no evidence 
of the peculiar teeth of Nucula. The shape and obliquity of the lines of growth show 
a relationship to OC. aquilina, the shell of greatest range in this group, but the two 
forms are easily distinguished. I have visited the locality myself this summer 
and obtained a number of specimens, some of which showed the interior. The 
accessory anterior adductor muscle scar is above the anterior adductor, as in 
other members of this genus. The hinge is without cardinal teeth, but there is 
an approach towards a flattened hinge-plate seen as an expansion down- 
wards of the edge of the shell, more easily seen in casts; the groove for the 
ligament is apparent, but I have not seen any specimens with the ligament 
preserved. In the bed at Kilrenny Mill the shell occurs in great numbers though 
the horizontal distribution seems limited to a few inches, and a mytiliform shell is 
very abundant, which I expect is the form named by R. Etheridge, jun., 
Anthracoptera ? obesa ;' but I hesitate to refer it to this genus (Naiadites) because 
in addition to the striated hinge-plate it possesses a well-marked tooth in the 
hinge. I would point out that Mr. R. Etheridge, jun.,’ doubtfully refers a shell 
from the cement stone group of Craiglockhart Hill, near Edinburgh, to Anthra- 
cosia ? (Unio) nucleus, Brown, to which I have alluded on p. 638, the original 
locality being Woodhall, Water of Leith, and it is very possible that it and the 
Species under discussion are the same. 
1 “Quart. Journ. Geol. Soc,’ vol. xxxiv, 1878, p. 12, pl. 1, figs. 12 and 18, (14?). 
* Ibid, p. 16, pl. 2, fig. 20. 
