122 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 
Unios, which was not mentioned by name, Phillips says, ‘* Williamson has maccu- 
rately referred this shell to Unio nuciformis” [of Hibbert]. The second Unio is 
named Unio linguiformis = Unio Phillipsti, Williamson, although no grounds are 
given for this apparently arbitrary change of name, in spite of a description, though 
meagre, having been published, part of which I have quoted above. It is to 
be noted that Mr. R. Etheridge, in his redescription of this species (op. supra 
by 
cit.), adds ‘‘ without description”? to his reference to Willamson’s original 
publication : quoting him, I fell into the same error in my former paper. 
Williamson only describes one shell, but mentions later in his paper remains 
which had been mistaken for fish scales, measuring about a quarter of an inch 
across. But it is the shell which he refers to Unio nuciformis and calls Unio 
Phillipsii. Moreover this species cannot be said to have a ‘ hinge-line (which) 
deviates very little from parallelism to the front lines of growth.” Indeed, 
Phillips’s first Unio shell appears from the description to correspond better with 
Williamson’s form. Neither Professor Rupert Jones nor Mr. R. Etheridge, jun., 
noticed this curious mistake of Professor Phillips, both authors giving Unio 
linguiformis as a synonym of Anthracomya Phillipsii. 
The original specimen being that of a shell crushed flat, it is difficult to judge 
what exactly would be the form of uncrushed examples. I have referred fairly 
perfect shells from the horizon of the Knowles ironstone to this species, Pl. XVI, 
figs. 11—13, one of which (fig. 11) is a cast, and the exact outline of the shell cannot 
be seen on account of imperfections of the extreme anterior portion and the 
posterior border. The others (figs. 12 and 13) would, I think, if crushed flat, 
exhibit a similar form to those of A. Phillipsii, which occur in such numbers in 
the higher beds. 
If I am correct in my reference, A. Phillipsii was a fairly tumid shell, so gently 
tumid that the diagonal ridge so characteristic of the genus is not apparent ; and 
this view is supported by an observation by Mr. EK. W. Binney, that in the 
uncrushed state the shell closely resembles a Modiola. This is so, speaking broadly, 
but the position and shape of the umbones are characteristically different from 
that which obtains in Modiola. I have recently obtained both crushed and 
uncrushed specimens of this species from the Speedwell pit, Gloucestershire. In 
these shells the oblique ridge is more acute, and not so gradually gibbose as in the 
forms from the Knowles Ironstone, Fenton. 
The shell seems to occur at several horizons in the Bristol district, judging 
from the matrix in which they occur, but I am unable to give the exact beds. 
This is, I believe, a new discovery (the shells were collected by Mr. Stock, of 
Bristol), and an interesting one, as molluscan remains are very rare indeed in this 
coal-field. 
In crushed examples it is often very hard to distinguish between Anthracomya 
