BRACHIOPODA. 
57 
while in Lingulella the opening for the passage of the pedicle is a sharply de¬ 
fined slit, not merely making a depression upon the sur¬ 
face of the cardinal area, but apparently penetrating it 
from apex to cardinal line Varying conditions of pres¬ 
ervation will often make the determination of this feature 
difficult; but, aside from the character of the cardinal 
area, there is little known of the type-species of Lingu- 
lella which can be satisfactorily regarded as of generic value. # Mr. Salter 
suggested a similarity in the muscular scars of L. Davisi, and those of Obolus 
and Obolella ; Davidson, however, was unable to find examples of the species 
showing these impressions satisfactorily,! but called attention to the coarse 
punctae over the visceral surface of one individual. 
The generic term Lingulella has been used with considerable freedom by 
both American and English writers, but while there must remain a degree of 
uncertainty in regard to the correct generic character of many species now in¬ 
cluded under this name, there are a few primordial forms which are pretty well 
understood, both externally and internally; hut whatever conclusions in regard 
to the generic features of Lingulella are derived from the study of these, 
must be dependent upon the results of future investigations upon the type- 
species, L. Davisi. 
Mr. C. D. Walcott has given! figures of Lingulella Ella , Hall and Whitfield, 
which show not only the characteristic cardinal area and pedicle-slit, but 
give very distinctly the character of the muscular impressions on both valves. 
There will also be found on Plate ^ figs. 1-4, of this volume, illustrations of 
the interior of both valves of Lingulella ccelata, Hall (Orbicula, Hall, 1847, 
* Dr. King was strongly disinclined to admit the term Lingulella. In his work upon the “ Characters 
of Lingula anatina,” he says: “The deltidium is a variable structure in Palliobranchs generally; and 
its modifications are far from being understood. As regards the deltidium in the genus under consideration 
[Lingula], one circumstance is remarkable: it has been in a great measure overlooked ; at least I can find 
little, or rather no notice of it in the writings of previous observers. It is this oversight which led the late 
J. W. Saltek to institute his genus Lingulella, which he typified with the Cambrian Lingula Davisi, under 
the belief that its ‘pedicle-groove’ and ‘ hinge-area ’ do not characterize any species of the old Bruguierian 
genus” (Ann. and Mag. Nat. Hist., Fourth Ser., vol. xii, p. 14. 1873). 
f Silurian Brach., p. 55. 
I United States Geological Survey, Bull. 30, pi. vii, fig. 2; and pi. viii, figs. 4 a, b, c. 1886. 
