156 
surface is convex and smooth, as in the several species 
just described ; from all of which, except T. platyloba, 
(which is known by its flatness,) it is distinguished by 
the lateral plaits. 
All the figures are of specimens from Ireland, except 
fig. 6, which is taken from one found in Derbyshire. 
Were it not that we possess the individual specimen 
Mr. Martin figured, we should, notwithstanding the ac- 
curacy of his figure, have been in some doubt regarding 
its identity with the species before us ; but we find its 
blunt form to arise from distortion, caused by several very 
evident fractures. Terebratula lateralis M. C. (tab. 83, 
f. 1,) is probably a variety of T.Pugnus, although it have 
only three plaits : however, the difficulty of distinguish- 
ing which are species, and which are varieties, is so 
great in this variable division of Terebratulae, that I can- 
not speak positively. Figs. 3, 4, and 5, upon the present 
plate, are very nearly related to T. platyloba upon the 
last plate, and seem to point out that as a variety only of 
T. Pugnus. The number of plaits, the form and general 
aspect even, is so inconstant, that out of several hun- 
dred specimens hardly two can be found alike. Those 
with lateral plaits are the most variable, and might per- 
haps be divided into more species ; but it would be diffi- 
cult to assign the boundaries. On the other hand, the 
T. inflata is in general recognised immediately by its 
form. 
In the Encyclopedic Methodique (tab. 245, figs. 6 and 
7) are figures of a Terebratula with lateral but no cen- 
tral plaits. Can this be a variety of either of the Irish 
species ? 
