74 PERMIAN FOSSILS. 
Productus, which, on account of its never displaying either a foramen or fissure, might 
be supposed to be unprovided with a pedicle; but as this part, as will shortly be seen, 
affords attachment to several muscles, it seems unsafe to predicate its absence in any 
palliobranchiate genus whatever, but particularly in one intimately related to forms 
(e. g. Strophomena and Leptena) which undoubtedly possessed it. 
The pedicle may be said to serve two purposes: jirst, the mooring of the 
shell to foreign bodies; and, second, as a muscular fulcrum. In the imperforate 
Strophomenas and Leptznas it can only have occupied the latter office, since the 
fissure is either closed with a deltidium, or completely filled up with the boss of the 
opposite valve ; but in the perforated species, as Strophomena alternata, Leptena analoga, 
&c., it is clear that the pedicle has served both purposes. The simple office, that is, 
its answering as a base of attachment for certain-muscles, is the one I propose 
assigning to the pedicle of Productus. The same simple subserviency of the pedicle is 
evidenced in the non-foraminated Orthisinas (0. plana, O. hemipronites) and Stropho- 
menas (S. rugosa = (?) planumbona) ; while it is duplicated in such congeneric species 
as Strophomena alternata and Orthisina Vernewli. Yrom the foramen becoming closed in 
old shells, it must be concluded that the pedicle, as a mooring instrument, was dispensed 
with in old age: my large specimens of Leptena analoga show the foramen distinctly 
closed. In young examples of Strigocephalus Burtint the pedicle passed through an 
open fissure, as in many Spiriferidias ; in individuals of a more advanced age, it passed 
through a foramen in the deltidium, which had gradually filled up the fissure; while 
in those full grown, it was dispensed with, as proved by the filling up of the foramen 
as well. 
In the perforate valve of Waldhewmia Australis three pairs of muscles pass from the 
inside, a little in advance of the upper end of the pedicle, to different situations. The 
outermost pair, which consists of the muscles implanted nearest the sides of the 
valve, passes at a slight angle into the upper part of the pedicle (Pl. XX, figs. 10, 
12 6). Within these muscles, and somewhat in front of them, another pair 
(Pl. XX, figs. 10, 12c) passes downwards, slightly converging at the same time, 
and becomes attached to the boss on the hinge of the imperforate valve (Pl. XX, 
figs. 11, 12). To distinguish these two pairs of muscles from each other, it is 
proposed to name the former the superior pedicle muscles, and the latter the cardinal 
muscles. 
A little in front of the superior end of the pedicle, and a little behind and within 
the attachment of the cardinal muscles, and therefore near the medio-longitudinal line 
of the perforate valve, is implanted the remaining pair, which passes directly down to 
a little behind the centre of the imperforate valve; each muscle, at the same time, 
becoming dichotomous in its inferior half (Pl. XX, figs. 10, 12d): these may be 
termed the valvular muscles. In addition to the cardinals and the valvulars, the 
imperforate valve affords attachment to other two muscles, which pass upwards from 
