204 PALEONTOLOGY OF NEW YORK. 



the Upper Devonian of Iowa ;* R. Missouriensis, Sliuiiiard, and R. striato-costata. 

 Meek and Worthen, 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. Ealoniiformis, McChesney, and the Camarophoria Sivalloviana, 

 Shumard, of the Upper Carboniferous limestone. 



Shells of this type of exterior abound in all later palaeozoic faunas. 



Genus EATON I A, Hall. 1857. 



PLATE LXI. 



1841. Atrypa, Cokkad. Ann. Rept. Palsont. Depl. N. Y. Geol. Survey., p. 66, 



1842. Atrj/Tpa, Vandxem. Geology of N. Y. ; Rept. Third Dist., pp. 120, 121, figs. 4, 5. 



1843. Atrypa, Mathbb. Geology of N. Y. ; Rept. First Dist., p. 342, fig. 3 ; p. 343, figs. 3, 4. 

 1843. Atrypa, Hall. Geology of N. Y. ; Rept. Fourth Dist., p. 148, fig. 3. 



1867. Batonia, Hall. Tenth Ann. Rept. N. Y. State Cab. Nat. Hist., pp. 90-92, figs. 1-7. 



1859. Batonia, Hall. Twelfth Ann. Rept. N. Y. State Cab. Nat. Hist., pp. 35-37, figs. 1-7. 



1859. Eattmia, Hall. Palseontology of N. Y., vol. iii, pp. 241-243, 432-488, pi. xxxvii, figs. 1 o-y, 



2 a-c; pi. xxxviii, figs. 14-26; pi. ci, figs. 1, 2j pi. cia, figs. 2-6. 

 1866. Batonia, Mbbk and Worthbn. 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 Rhynchunella alta, Calvin, which some American writers have considered equivalent to R. pug- 

 niu, Martin, is a local form retaining quite peitdstently the features of II. 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 actt.minata\\ke fold than the latter. The fact that the New York shell evinces gradations 

 in form which include both the pugnus and the acuminata type 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 other writers, who nevertheless note the great variability of the shells 

 {lassing under these two names. That it may be convenient to retain both terms is undoubtedly true, but 

 the ]>a8sage of one series of foi-ms into the other is quite as apparent among the Devonian as among the 

 Carboniferous shells. It may be a fair question whethev the Devonian shells passing as R. pugnus and R. 

 acuminata ai-e entitled to these names ; whether, for instance, it would not be belter to retain Phillip's 

 name, R. anisodonta, for the former, and, possibly, R. triangularis, Sowerby, foi- the latter. In both of the 

 former cases the originals were from the Carboniferous limestone of Dei-byshire and attained, as a usnal 

 habit, a much greater size than the Devonian shells. The American Carboniferous shells representing the 

 specific type of y{. pugnus, namely, R. striato-costata. Meek and Worthen, R. Missouriensu!, Shumard, bear 

 a fine ra<iiate-lineate ornamentation, and what might be interpreted as a similar chara<;ter is apparent in 

 many of Davidsok's figui-es of the Carboniferous species (Carboniferous Brachiopoda, pi. 22), though this 

 feature iii not mentioned in bis descriptions. The same character is highly developed in the Devonian species, 

 R. Ueyendorfi, de Vei-neuil, a sharply acuminate shell without plications. 



