BRACHIOPODA. 
75 
ward and backward. These callosities are strongly suggestive of the appear¬ 
ance produced by the combined lateral and central scars in Oboldla chromatica 
and O. crassa, and it is probable that the}*- represent the same features, in which 
case the posterior depressed area is to be regarded as the progressive track of 
the centrals, its anterior margin advancing with age. 
The position of the valve lying between the anterior horns of the lateral 
semilunes is also deeply depressed, but its surface shows no markings. The 
specimens of L. lepis from the Cincinnati rocks appear not to have retained 
these lateral callosities, but they are faintly developed in the New York exam¬ 
ples of the same species. 
In the brachial valve, the cardinal area has about the same degree of devel¬ 
opment as in Obolella, and is also distinctly grooved. The muscular scars in 
this valve are poorly defined, but their limits are probably indicated in part by 
the septa, which in L. lepis are three in number; one in the axial line larger 
than the rest, and one on either side. All these ridges appear to be bifurcated 
at their anterior extremities, in the axial ridge the faint duplication beginning 
at about the center. In the Utica slate specimens of L. lepis the lateral ridges, 
in the only satisfactory example observed, appear to be curved inward toward 
their extremities, as they also are in L. insignis where they attain a very con¬ 
spicuous development, uniting with each other in front and being separated 
from the margin of the shell only by a low furrow. These ridges may be re¬ 
garded as the curved fulcra of the lateral muscles. 
The features seen in Leptobolus indicate its close alliance to Obolella, but 
are at the same time so diverse from those of Obolella chromatica that the forms 
can not be regarded as congeneric. 
Genus ELK AN I A, Ford. 1886. 
PLATE III, FIGS. 15-19. 
1862 Obolella, Billings. Palaeozoic Fossils, vol. i, p. 69, fig. 62 a, b. 
1884. Obolella?, Walcott. Palaeontology Eureka District, p. 67, pi. i, fig. 2. 
1886. Billingsia, Ford. American Journal of Science, vol. xxxi, p. 466. 
1886. Elkania, Ford. American Journal of Science, vol. xxxii, p. 325. 
This genus has been established by Mr. S. W. Ford upon the late Mr. Billings’ 
species, Obolella desiderata , from the Graptolite shales at Pointe Levis. We have 
