BRACHIOPODA. 
advena* * * § These are all from the Etage D, and should they prove referable to 
Obolella, will constitute the latest recorded appearance of the genus. 
The American species which can safely be classed as Obolella are the fol¬ 
lowing : 0. chromatica, Billings, 0. crassa, Hall, 0. Circe Billings, O. gemma , 
Billings, and probably 0. polita,-\ Hall.i: Of other species referred to the genus 
by American writers, it may be remarked: 
0. ? ambigua, Walcott,§ will probably prove referable to the genus Elkania, 
as suggested by the author of the genus, Mr. Ford.|| 
0. ccelata, Hall, = Lingulella ccelata (Orbicula ccelata , HallH). 
0. cingulata, Billings, = Kutorgina cingulata. 
0. desiderata, Billings,** * * §§ is the type-species of Elkania. 
0. ? discoidea, Hall and Whitfield ;ff generic character in doubt, as the interiors 
are not known. 
0. ? Ida, Billings,H is imperfectly known. 
0. ? misera, Billings,§§ is referred to the genus Linnarssonia, by G. F. 
Matthew.|||| 
O. nana, Meek and Hayden.1® Mr. Walcott is disposed to consider this 
* Syst. Sil. Boh6me, pi. 95, fig - , iv. 
t The Lingula prima (Conrad’s MS. description, first published by Hall, Pal. N. Y., vol. i, p. 3. 1847), 
from the Potsdam quartzite at Ausable Chasm, N. Y., has been referred by Mr. Whitfield (Bull. American 
Museum Nat. Hist., vol. i, No. 5, p. 142. 18S4) to the genus Obolella, and is also identified by him with 
the species 0. f polita, Hall, from the yellow pulverulent sandstones at Trempaleau, Wisconsin, so that, 
should this identification hold good, the latter name will become a synonym of the former. The identifica¬ 
tion is, however, made solely on the basis of external similarities, and must be regarded as subject to such 
modifications as the interior characters, when known, may require. These have not been satisfactorily 
demonstrated in the New York species, but there are specimens before us which indicate that its muscular 
impressions are more nearly those of Lingulella than of Obolella. The Obolella nitida of Mr. S. W. Ford, 
also considered by Mr. Whitfield a synonym of the same species (op. cit.), appears, from an examination 
of the type-specimens, to be a totally distinct fossil. 
{ Under the name Obolella Atlantiea, Mr. Walcott has mentioned, without giving a detailed description, 
an additional species from the Olenellus zone, Conception Bay, Newfoundland (Proceedings U. S. National 
Mus., vol. xii, p. 36. 1889). 
§ Palaeontology Eureka District, p. 67, pi. i, figs. 2 a-c. 1884. 
|| American Journal, vol. xxxi, p. 467. 1886. 
If Palaeontology N. Y., vol. i, p. 290, pi. lxxix, fig. 9. 
** Palaeozoic Fossils, vol. i, p. 69. 1862. 
ft Geographical and Geological Exploration Fortieth Parallel, p. 205, pi. i, figs. 1, 2. 1877. 
Palaeozoic Fossils, vol. i, p. 71, figs. 63 a, b. 1862. 
§§ Palaeozoic Fossils, vol. ii, p. 69. 1874. 
1111 Illustrations Fauna St. John Group, No. iii, p. 35. 1885. 
Palaeontology Upper Missouri, p. 4, pi. i, figs. 3 a-d. 
