HYDE: CAMAROPHORELLA. 59 
detail as in Camarophorella and no comparison is possible. Further, 
the jugum of Camarophorella differs more from those of the others 
than they do among themselves. In Merista, Meristella, and Dioris- 
tella, which are the only ones figured, the branches of the primary 
lamellae that "unite to form the stem" are much longer than in 
Camarophorella. The lamellae of the jugum are smaller and do not 
enter the space between the primary and secondary lamellae of the 
spiralia as in Camarophorella. These two differences alone serve 
to render the two types profoundly different in aspect. 
Camarospira is the only genus in the subfamily that possesses 
a spondylium in the brachial valve similar to that of Camarophorella. 
However, Hall and Clarke ('95, p. 82) state that the pedicle muscles 
only are attached to this platform, the adductors and diductors being 
attached directly to the shell in both valves. There is a median sep- 
tum in the brachial valve. The difference in the muscular attachment 
renders further comparison useless. 
Merista, the known forms of which are confined to the lower Devon- 
ian in this country but are found also in the Upper Silurian (Wenlock) 
of Europe, is characterized by a spondylium or "shoe-lifter" in the 
pedicle valve and a median septum in the brachial valve. The spondy- 
lium is of an unusual t^'pe (pi. 10, fig. 57-59, after Hall and Clarke). 
"Between the dental plates is an arched free plate (the 'shoe-lifter' 
process) attached by its posterior and lateral margins, but at its anterior 
margin extending beyond the dental lamellae and rising in a low broad 
curve .... The muscular area appears to be limited to the space be- 
tween the dental lamellae and to the surface of the 'shoe-lifter ' " (Hall 
and Cla. ke, '95, p. 70). There is no median septum supporting this 
platform. 
A few Middle Devonian forms in Europe, possessing this structure 
and formerly included under Merista, were found by Hall and Clarke 
('95, p. 72) to "possess a 'shoe-lifter' quite as conspicuously developed 
in the brachial as in the pedicle valve, while the cavity beneath it is 
divided into two compartments by the median septum which extends 
beyond the anterior edge of the platform thus formed." To these 
the name Dicamara was given. This structure which is much the 
same as that seen in the brachial valve of Camarophorella, is shown in 
figure 60 (pi. 10), after Hall and Clarke. 
Dicamara with its brachial platform, thus approaches more closelv 
to Camarophorella than any other known form, but on first considera- 
