I 



ANIMALS. 75 



the crural base (where each one is divided), and become inserted in the upper part of 

 the pedicle (PI. 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 Waldlieimia Australis characterised the genera 

 Productus, Leptana, Orthis, 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 (PI. IX, fig. 7 b), 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 ; indications of something of the kind are, however, 

 observable on sharp casts of Froductus horridus (PI. XI, fig.' 1 e) ; and I am inclined to 

 think that the marks occasionally seen on the socket-ridges of Scldzoplioria Micltelini are 

 due to these muscles. Considering the faintness of the impressions of the inferior pedicle 

 muscles in Waldlieimia Australis, 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 Froductus. 

 Guided by the muscular system of Waldlieimia Australis, I am led to conclude that the 

 two large striated impressions on the convex valve of Froductus giganteus (PL XIX, 

 fig. 2 a) 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 adjoining 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 (PI. XIX, fig. 1h, c; vide explanation of PI. XIX) : they 

 are often undefinable and confluent (PL XI, fig. 15 3; PL XII, fig. 3 a) ; 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 Waldlieimia 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 oi Anemia epliippium produces a similar dendritic impression (PL XX, 

 fig. 8 a). The three pairs of impressions to be seen on the saucer-shaped process in 

 the perforate valve of Leptana analoga (PL XX, fig. 6/, g, li) may also be referred to 

 the pedicle, cardinal, and valvular muscles, since they hold nearly the same relative 

 position as those of Froductus giganteus. 



