ANIMALS. 75 
the crural base (where each one is divided), and become inserted in the upper part of 
the pedicle (Pl. XX, figs. 10, 12e): it is proposed to name these the inferior 
pedicle muscles. 
From an examination of a number of palliobranchiate shells, I feel persuaded that 
a muscular system similar to that of Waldheimia Australis characterised the genera 
Productus, Leptena, Orths, and several others. In the large or corresponding valve 
of these shells, there are impressions answering to the six muscles which have been 
described as passing from the perforate valve; and in the opposite valve there are 
impressions answering to the four inferior divisions of the valvulars ; and the hinge is 
either furnished with a boss or an excavated part (Pl. IX, fig. 7 4), having a surface 
displaying evidence of muscular attachment. 
I am not decided as to the existence of impressions in any of the fossils named, 
resulting from the inferior pedicle muscles, that is, those passing from the crural base 
to the upper part of the pedicle ; mdications of something of the kind are, however, 
observable on sharp casts of Productus horridus (Pl. XI, fig. 10 e); and I am inclined to 
think that the marks occasionally seen on the socket-ridges of Schizophoria Michelini are 
due to these muscles. Considering the faintness of the impressions of the inferior pedicle 
muscles in Waldhemia Austrahs, it need not be a matter of surprise how few and slight 
the indications of their presence are in specimens found in a fossil state. 
The impressions just noticed are best seen on casts of certain species of Productus . 
Guided by the muscular system of Waldheimia Australis, 1 am led to conclude that the 
two large striated impressions on the convex valve of Productus giganteus (Pl. X1X, 
fig. 2a) are due to the superior pedicle muscles: the linear impressions often 
observable converging from them towards the umbone, show that the muscles belonging 
to them have been in close contact with the inner surface of the large valve: this 
circumstance, their size and position relatively to the adjoming muscular impressions, 
constitute a powerful argument in favour of the view stated. 
Within the impressions of the pedicle muscles, and on a flattened elevation, are 
situated four other impressions (Pl. XIX, fig. 24, c; vide explanation of Pl. XIX): they 
are often undefinable and confluent (Pl. XI, fig. 154; Pl. XII, fig. 3); but occasionally 
specimens exhibit them separated. The peculiar dendritic character of these impres- 
sions has induced many to conclude that they were produced by the viscera; but from 
the fibres of the muscles of Waldheimia Australis possessing a dendritic arrangement, 
and thereby being capable of producing similar impressions under proper circumstances, 
this view has been materially divested of the principal argument adduced in its favour. 
The stopper muscle of Anomia ephippium produces a similar dendritic impression (Pl. XX, 
fig. 82). The three pairs of impressions to be seen on the saucer-shaped process in 
the perforate valve of Leptena analoga (Pl. XX, fig. 67, g, 4) may also be referred to 
the pedicle, cardinal, and valvular muscles, since they hold nearly the same relative 
position as those of Productus giganteus. 
