432 Mr. R. Etheridge on Carboniferous Lamellibranchiata. 
naving been gregarious ; but the specimens from Fife were in 
better preservation, and he intended to have them laid open 
and submit them to a careful examination in order to deter- 
mine the generic characters. Circumstances prevented this, 
but it has now been made clear by Mr. Salter.” Many years 
ago Dr. Rhind figured, but did not describe, under the name 
ot Axinus Pentlandicus*, two shells from Woodhall (probably 
the Colinton of the above quotation), which I believe to be 
specifically distinct from one another. One of these} was after- 
wards refigured and described by Capt. 'T’. Brown as Pachyodon 
pyramidatus{, without any reference to Rhind’s figure, and 
again as Unio pyramidalus§. [am at present under the im- 
pression that Rhind’s fig. 6 and Brown’s P. (Unio) pyramidalus 
are the same shell as the present species, which I have ven- 
tured to describe under the name of S. Salter’, in memory of 
an early preceptor and friend to whom [ am indebted for many 
pleasant rambles and much profitable instruction. The pos- 
terior slope of iS. Saltert is very frequently broken or crushed 
away, when the individuals bear a close resemblance indeed 
to the above shells, in which there is no slope figured, the 
posterior side consisting of a blunt acumination. If future 
investigation should prove them to be identical, Capt. Brown’s 
specific name will have to be adopted. The Rev. Thomas 
Brown has most obligingly allowed me to examine the original 
specimens in his cabinet used by Mr. Salter for the woodcuts 
cited above. Of these, fig. 1 represents the internal umbonal 
region of the right valve, and shows the anterior tooth of the 
natural size. In fig. 2 we have a view of the whole of the 
interior of the left valve, with an enlarged drawing of a 
portion of the hinge, and showing the plain surface and wedge- 
form of the tooth, which in some Schizodontes is bifid. The third 
figure is a good external representation of the left valve, with 
the general characters well indicated, except that the lamin 
of growth on the upper half of the shell are too pronounced. 
It is an enlarged figure, although the species frequently 
reaches the size indicated. In the thick undivided nature of 
the central tooth of the left valve, S. Salter? quite agrees with 
two other Carboniferous species in which the dental arrange- 
ment has been noticed—S. carbonarius, Sow., and S. axint- 
formis, Phil.; in both of these the corresponding tooth is 
simple and thick ||, thus presenting a marked difference from 
* Age of the Earth, t. 2. f. a & 6. 
i RE 
{ Annals Nat. Hist. 1845, xii. p. 396, t. 16%. f. 9. 
§ Fossil Conchology, p. 179, t. 73. f. 19. 
| King, Mon. Perm. Foss. p. 187. 
OI 
