BRACHIOPODA. 205 



Conrad.* The former has a very considerable range, appearing, according to 

 DavidsonI in the Caradoc, Lower and Upper Llandovery, Woolhope, Wenlock 

 and Ludlow formations. 



In America it has been found only in the Niagara group, while its congener, 

 Orthis varica, Conrad, a very distinct species,:j: is confined to the Lower Helder- 

 berg fauna. 



DALMANELLA 



Uioin. propo.-?). 



X. Group of Orthis testudinaria, Dalman. 



PLATE Vb, figs. 2o-39; and PLATE Vc, FIGS. 1-47. 



1828. Ortlm, Dalman. Kongl. Vet. Acad. Ilaiidl., pp. 115, 117, pi. ii, tif,'. 4. 



1842. Orthis, Emmons. Geology of N. Y. ; Rept. Second Dist., p. 404, tig. 4. 



1842. Orthis, Vanuxem. Geology of N. Y. ; Rept. Third Dist., p. 189, fig. 4. 



1843. Ortliii. Atrypaf UkhL. Geology of N. Y. ; Rept. Fourth Dist., p. 10,"), fig. t! ; ji. 17."), fig. 4, lunl 



p. 271, fig. 4. 

 1843. Orthis, Conrad. Proc. Acad. Nat. Sei., Pliila., vol. i, p. 133. 

 1847. Oi-this, Hall. Paleontology of N. Y., vol. i, pp. 117, 118, 120, 128, pi. xxxii, tigs. 1, 2, 5, and pi. 



Ixxix, fig. 4. 

 1852. Orthis, Hall. Palieontology of N. Y., vol. ii, p. 152, pi. lii, fig. 3. 



1856. Orthis, Billings. Canadian Nat. and Geol., vol. i, p. 40, tig. 1, and p. 13ii, pi. 2. fig. 5. 



1857. Orthlt, Billings. Rept. of Progress Geol. Surv. Canada for 1856, )i. 21)6. 



1857. Orthis, Hall. Tenth Rept. N. Y. State Cab. Nat. Hist., p. 42, figs. 1, 2, and p. 44, tig. 1. 



1859. OrthU, Hall. Palseontology of N. Y., vol. iii, pp. 168-172, pi. xii, fig.s. 1-21, and pi. xiii, figs. 1-12. 



1859. Orthis, Billings. Canadian Nat. and Geol., voi. iv, p. 434, fig. 10. 



1860. Orthis, F. Roemer, Sil. Fauna westl. Tennessee, p. 62, pi. v, fig. 7. 

 1860. Orthis, Hall. Thirteenth Rept. N. Y. (^tate Cab. Nat. Hist., p. 121. 

 1862. Orthis, Hall. Geology of Wisconsin, vol. i, p. 42, fig. 7 and p. 436. 

 1862. Orthis, Billings. PaliBOzoic Fossils, vol. i, p. 79, fig. 72. 



1862. Orthis, Hall. Fifteenth Rept. N. Y. State Cab. Nat. Hist., pi. ii, figs. 1-3. 



1863. Orthis, Billings. Geology of Canada, pp. 130, 165, 231, 312, figs. 57, 144. 246, 320. 



1867. Orthis, Hall. Palaeontology of N. Y., vol. iv, p. 35, 46, 62, pi. v, figs. 1, 2; pi. vi, fig. 1 and 



pi. viii, figs. 3-8. 



1868. Orthis, Meek and Worthen. Geology of Illinois, vol. iii, p. 373, pi. vii, tig. 6. 



1873. Orthis, Meek. Paleontology of Ohio, vol. i, pp. 103, 109, 112, pi. viii, figs. 1-3, 5. 



1874. Orthis, James. Cincinnati Quart. .lour. Sci., vol. i, p. 19. 



1875. Orthis, Millbb. Cincinnati Quart. Jour. Sci., vol. ii, pp. 20, 22, 24, 30. 



*The Orthli acutiluba of Ringdebebg is a form of 0. biloha in which the lobes are veiy ilivergent. All 

 stages of variation between this extreme and the normal form for the species are readily detected in any 

 large collection. 



+ British Silurian Brachiopoda, p. 208. 



I Davidson (Silurian Brachiopoila, p. 207) and Quenstedt (Petrefactenkunde Deutschlands, pi. Iv. figs. 

 67-70), erroneously regarded this species as indentical with 0. biloha. 



