Ii- Etheridge, Jan. — Contributions to British Palceontology. 245 
1868, p, 204, fig. 44. Anthracomya ( Naiadites ) he vis, Salter, Quart. Journ. Geol. 
Soc., 1863, vol. xix. p. 79, fig. 2. Also Unio nuciformis, Hibbert, Trans. R. Soc. 
Edinb., 1836, vol. xüi. p. 245.) 
Sp. Chars. — Obliquely-broad-ovate, flattened, abruptly truncated 
along the dorsal margin. Anterior end rounded ; posterior end pro- 
duced ventrally, its margin obliquely rounded. Hiuge-line not so 
long as the shell, passing insensibly into the oblique posterior 
margin. Umbones anterior, but not terminal, inconspicuous. Shell 
marked with exceedingly close fine microscopic thread-like strite, 
with a few transverse wrinkles, which at times give it the ap- 
pearance of being partially radiately striated. 
Obs . — A small shell was described by Dr. Dawson from the Coal- 
measures of the South Joggings, Nova Scotia, under the name of 
Naiadites leevis (= Anthracomya, Salter), to which the present shell 
bears so strong a resemblance that I was for some time quite at a 
loss how to distinguish between them. However, A. Scotica is larger 
than the Nova Scotian Naiadites leevis. Judging from Dr. Dawson’s 
figure, the concentric striaa are also more numerous, finer and closer ; 
the posterior end appears to be more obliquely truncate, and the 
beaks are more anterior. 
In pointing out the resemblance between these two forms, I am 
supported by the opinion of Prof. T. Eupert Jones, F.R.S., who, 
independently of any views of my own, suggested a reference of 
the Scotch fossil to Dr. Dawson’s species. It is sufficiently distinct 
from the other Anthracomya and Naiadites described by Mr. Salter , 1 
and Dr. Dawson , 2 not to require comparison ; but it appears to be 
related to Anodonta obstipa, Ludwig . 3 Judging from figures only, 
A. Scotica also resembles the shell figured by Prof. T. E. Jones 
as the probable young of Anthracomya Phillipsii, Will .; 4 but the 
concentric strirn are much closer and the shell larger, as Prof. Jones’s 
figure is highly magnified. Dr. Hibbert long ago obtained, from 
strata connected with the Burdiehouse Limestone, a shell to which 
he gave the name of Unio nuciformis . 5 Hibbert’s figure represents 
a shell in the uncrushed state of a particularly convex and globose 
form. All our efforts to re-discover this shell have failed hitherto ; 
and as Dr. Hibbert’s collection was brought to the hammer, I am 
afraid little chance remains of our ever being able to obtain access 
to the type, although I have tried all means at my disposal. The 
thought has often struck me wketker this species might not be Unio 
nuciformis in a perfectly flattened form, its usual condition. Al- 
though some of the characters bear out this supposition, still, I 
have seen no evidence in the flattened examples of A. Scotica of 
t he great inequality of the valves exhibited by Dr. Hibbert’s figure. 
Loc. and Horizon. — The figured example is from the Linnhouse 
Water between Calder Hall and Calder Wood, near Mid Calder, 
1 Iron Ores, Great Britain, pp. 230-1. 
2 Acadian Geologv, 2nd ed., p. 204. 
3 “ Freshwater Shells of the Coal-formation of the Urals,” Palceontographica , 
vol. x. t. 3, f. 2. 
4 Geol. Mag., Vol. VII. PI. IX., Fig. 18. 
6 Trans. R. Soc. Edinb., vol. xiii. p. 245. 
