BRACHIOPODA. 
61 
there is no doubt that the conspicuous laterals correspond more or less exactly 
with the laterals, and the central scar with the centrals in Lingula. Lingulepis 
also bears a broad and low median ridge, elevated along its margins and de¬ 
pressed in the middle, similar to, but fainter than that in L. anatina. Although 
the similarity to Lingula in these respects is evident, a much closer homology 
is found in the muscular scars of this valve of Lingulepis and that of Lingulella. 
This is seen in the crescentic laterals and the prominent central in Lingulella. 
In Obolella, the posterior coalescence of these scars is even more prominently 
developed than in Lingulella. 
In the muscular scars of the brachial valve, the divergence from Lingula is 
still more marked. These impressions make a conspicuous flabelliform scar, 
extending medially about one-half the length of the shell. The central portion 
of this scar is accompanied on either side by broader, partially resolvable lateral 
scars, all the subdivisions of the impression coalescing in the umbonal region. 
Here the crescentic laterals of Lingulella and Obolella are quite absent, but the 
posterior coalescence of all the scars into one broad and ill defined impression, 
is a feature noticeable in all of these genera. Thus the genus Lingulepis affords 
an important connecting link between Lingula and Lingulella in the direct line 
of relationship to Obolella and its allied genera. 
The shell-structure of Lingulepis is, presumably, closely similar to that of 
Lingula, and, as usually in that genus, its surface-ornamentation is uniformly 
of concentric lines. L. pinniformis also shows a few faint radiating lines, which 
are more strongly developed on the internal surface over the anterior portion 
and on the interstitial lamellae of the shell. 
The genus, as far as known, is represented only in American primordial 
faunas ; L. pinniformis, of the Potsdam sandstone of Minnesota and Wisconsin, 
finds a closely allied species in L. antiqua, Hall, of the same formation in New 
York. Two species, L. cuneolus and L. perattenuata, have been described from 
the Black Hills, by It. P. Whitfield , 1 * and in the same year Hall and Whit¬ 
field-)- referred three species to this genus, L. Ella, L. Mcera and L. ? minuta. 
The first of these has since proved a Lingulella, and it is probable that the 
* Preliminary Rept. Geology of the Black Hills. 1877. 
t King’s Report United States Geological Exploration Fortieth Parallel. 
