BRACHIOPODA. 75 



ward and backward. These callosities arc strongly suggestive of the appear- 

 ance produced by the combined lateral and central scars in Obolella chromatica 

 and 0. crassa, and it is probable that they 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 liorns of the lateral 

 semilunes is also deepiv depressed, but its surface shows no markings. The 

 specimens of L. lep/s from the Cincinnati rocks appear not to have retained 

 these lateral callosities, but they are faintly developed in tiie 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/., 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 i)y a low furrow. These ridges may be re- 

 garded as the curved fulcra of the lateral muscles. 



The features seen in Leptobolus indicate its clo.se alliance to Obolell.v, luit 

 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 in, FIGS. 15-19. 

 1862 Obolella, Billings. Palaozoic Fossils, vol. i, p. 69, tig. G2 ii, !>. 

 18S4. Obolella?, Walcott. Palffiontoloffy Eureka District, p. 67, pi. i, tig-. 2. 

 1886. BiUingsia, Fobd. American Journal of Science, vol. xxxi, p. 466. 

 1886. Elkania, Fokd. American Journal of Science, vol. xxxii, p. 32"). 



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 



