BRACHIOPODA. 
13 
passed closely about their insertion, a feature which requires confirmatory 
evidence. 
In so far, then, as the impressions upon the shell, left by the soft parts of the 
animal are concerned, we find a close correspondence in the existing and palae¬ 
ozoic members of this genus. 
We turn now to a consideration of the septal markings on the interior of these 
shells. When the soft parts are entirely removed from the shell of L. anatina, 
the pedicle-valve shows a broad, low, longitudinal ridge, whose margins are 
sharply incised along the posterior portion, but become elevated with the ele¬ 
vation of the entire ridge anteriorly. This ridge terminates in front of the 
center of the shell, and bears, at its excavate extremity, the impressions of the 
middle-lateral muscles, being buttressed on either side behind these, by the large 
scars of the centrals. From the posterior extension of this ridge diverge two 
more or less distinct longitudinal callosities, which are the inner boundaries of 
the transmedian impressions, or the raised margins of the parietal scars. In 
the opposite, or brachial valve, a longitudinal ridge is more or less developed 
toward the posterior portion of the shell, but becomes flattened over the 
central visceral region, whence it is produced much further forward than in the 
opposite valve, and is sharply elevated. Its terminal portion separates the ante¬ 
rior lateral scars, directly behind them lying the central muscular impressions. 
With these features in mind, we must expect to find the true palaeozoic Lingulas 
showing evidence, to a certain degree at least, of such internal ridges and cal¬ 
losities. In regard to these shell-ridges, King has said: “ The muscles, including 
the parietals, produce scars, often well seen in the valves of recent Lingulas. 
The scars are occasionally liable to become raised at their margin, giving them 
the appearance of individualized muscular fulcra or myophores. A specimen 
before us has the scar of one of the post-lateral parietals with its inner 
margin completely raised in the form of a plate. Such cases are evidently 
of abnormal formation; but they explain the origin of what may be assumed 
as normal cases—for example, Lingula albida, in which there are two of the 
same kind of plates. 
* On Some Characters of Lingula anatina. p. 8. 
