BRACHIOPODA. 
133 
ridge. The mutual relations of the different parts of the internal apparatus 
Fig. 120. Fig. 121 . 
Figs. 120, 121. The brachidium of Anoplotheca (Bifida) lepida. (c) 
Fig. 120. A lateral view, showing the relations of the loop to the median septum and ridge. 
Fig. 121. A posterior view from behind, 
are better seen in the accompanying constructive figures (120, 121), one 
representing a view of the interior from the side, the other from the umbonal 
region. 
This structure shows an admirable adaptation in the loop for resistance 
to strains; the slotted median ridge of the pedicle-valve is short and thick, 
extending for about one-half the length of the shell, and is most deeply 
excavated at the point where the stem of the loop is inserted. (See figure 
of the interior of this valve given on Plate LII, fig. 19.) The cardinal 
process in this species has not, so far as we are aware, been described or 
figured, but our sections show that it is quite similar to that of Anoplotheca 
venuka, as described by Sandberger and Suess. The latter species also has 
the median septum in each valve, and though the character of its loop is 
not known, it will be shown that in similar forms from American faunas this 
organ possesses the same structure as in Terebratula lepida. It is highly 
improbable that two species, so closely similar in external and internal 
characters as Anoplotheca venusta and Bifida lepida, and coexisting in the same 
fauna, are not congeneric. Therefore, with our present knowledge, it seems 
necessary to conclude that the term Bifida is altogether synonymous with 
Anoplotheca. 
