204 
PALEONTOLOGY OF NEW YORK. 
the Upper Devonian of Iowa;* R. Missouriensis, Shumard, and R. striato-costata, 
Meek and Wortlien, of the Choteau limestone; R. explanata, McChesney, of the 
Chester limestone; R. mutata, Hall, R. Ottumwa, White, of the St. Louis group; 
R. Uta, Marcou, R. Eatoniiformis, McChesney, and the Camarophoria Swalloviana, 
Shumard, of the Upper Carboniferous limestone. 
Shells of this type of exterior abound in all later palseozoic faunas. 
Genus E A T 0 N I A, Hall. 1857. 
PLATE LXI. 
1841. Atrypa, Conrad. Ann. Rej)t. Palseont. Dept. N. Y. Geol. Survey., p. 56. 
1842. Atrypa, Vandxem. Geology of N. Y. ; Kept. Third Dist., pp. 120, 121, figs. 4, 5. 
1843. Atrypa, Mather. Geology of N. Y. ; Kept. First Dist., p. 342, fig. 3 ; p. 343, figs. 3, 4. 
1843. Atrypa, Hall. Geology of IN. Y. ; Kept. Fourth Dist., p. 148, fig. 3. 
1857. Eatonia, Hall. Tenth Ann. Kept. N. Y. State Cab. Nat. Hist., pp. 90-92, figs. 1-7. 
1859. Eatonia, Hall. Twelfth Ann. Kept. N. Y. State Cab. Nat. Hist., pp. 35-37, figs. 1-7. 
1859. Eatonia, Hall. Palceontology of N. Y., vol. iii, pp. 241-243, 432-438, pi. xxxvii, figs. 1 a-y, 
2 a-c; jd. xxxviii, figs. 14-26; pi. ci, figs. 1, 2; pi. cia, figs. 2-6. 
1868. Eatonia, Meek and Worthen. Geol. Surv. Illinois, vol. iii, p. 396, pi. viii, figs. 2 a-d. 
Concavo-convex shells with median fold and sinus, and plicated or radiate- 
lineate exterior. Anterior margin deeply sinuate. From the beak of the 
pedicle-valve diverge two lateral cardinal ridges which limit a more or less 
distinct false area. On the interior the teeth are adnascent to the lateral walls 
* The Rhynchonella alta, Calvin, which some American writers have considered equivalent to R. png- 
nus, Martin, is a local form retaining quite persistently the features of R. anisodonta, Phillips {R. pugnus, 
var. anisodonta, Davidson). Though always smaller than the representatives of R. pugnus, occurring in 
the High Point (New York) fauna, at the base of the Chemung series, it less frequently shows a tendency 
toward the acute ac\iniinata-\\ke fold than the latter. The fact that the New York shell evinces gradations 
in form which include both the pugnus and the acuminata tyjie of exterior is but a further substantiation of 
the argument upon which McCoy, in 1852, reduced the latter to a variety of the former. This position has 
been contested by Davidson and othei’ writers, who nevertheless note the great variability of the shells 
passing under these two names. That it may be convenient to retain both terms is undoubtedly true, but 
the passage of one series of forms into the other is quite as apparent among the Devonian as among the 
Carboniferous shells. It may be a fair question whether the Devonian shells passing as R. pugnus and R. 
acuminata are entitled to these names; whether, for instance, it would pot be better to retain Phillip’s 
name, R. anisodonta, for the former, and, possibly, R. triangularis, Sowerby, for the latter. In both of the 
foi'iner cases the originals were from the Carboniferous limestone of Derbyshire and attained, as a usual 
habit, a much greater size than the Devonian shells. The American Carboniferous shells representing the 
specific type of R. pugnus, namely, R. striato-costata. Meek and Worthen, R. Missounensis, Shumard, bear 
a fine i-adiate-lineate ornamentation, and what might be interpreted as a similar character is apparent in 
many of David.son’s figures of the Carboniferous species (Carboniferous Brachiopoda, pi. 22), though this 
feature is not mentioned in his descriptions. The same character is highly developed in the Devonian species, 
R. Meyendorji, de Verneuil, a sharply acuminate shell without plications. 
