BRACHIOPODA. 269 



Genus TRIPLEGIA* Hall. 1858. 



PLATE XI C, FIGS. 1-22. 



1842. Terebratula, yoN Eichwald. Urwelt Russlands, vol. ii, p. 49, plate ii, figs. 6 a, b, c. 



1842. Atrypa, Emmons. Geology of N. Y. ; Rept. Second District, p. 395, tig. 6. 



1845. Sjjirifer, de Verneuil. Geol. Russ. et des Mont, de I'Oural, p. 149, pi. viii, fig. 7. 



1846. OrtMs, Producta, McCoy. Synopsis Silurian Foss. Ireland, p. 25, pi. iii, fig. 3; p. 30, pi. iii, fig. 12. 



1847. Atrypa, Hall. Paleontology of N. Y., vol. i, pp. 137, 139, pi. xxxiii, figs. 1, 2 ; pi. xxxiii*, fig. 1. 



1848. OrtMs, Phillips and Salter. Mem. Geol. Surv. United Kingdom, vol. ii, p. 289. 

 1852. Hemithyris, McCoy. British Palgeozoic Fossils, p. 201. 



1858. Triplesia, Hall. Twelfth Rept. N. Y. State Call. Nat. Hist., p. 44, figs. 1-3. 



1859. Spinfer, vou Eichwald. Leth»a Rossica, vol. i, p. 697. 



1859. Triplesia, Hall. Paleontology of N. Y., vol. iii, pp. 522, 523, figs. 1-3. 



(?) 1861. Camarella, Billings. Canadian Naturalist and Geologist, vol. vi, p. 318, fig. 3. 



(?) 1868. Camarella, Billings. Geology of Canada, p. 231, fig. 247. 



(?) 1865. Camarella, Billings. Palseozoic Fossils, vol. i, p. 220. 



1866. Orthis, Salter. Mem. Geol. Surv. United Kingdom, vol. iii, p. 697. 



1869. Triplesia, Davidson. British Silurian Brachiopoda, pp. 197-201, pi. xxiv, figs. 29, 31, 32, 



pi. XXV, figs. 3-5. 



1871. Orthis, Davidson. British Silurian Brachiopoda, p. 273, pi. xxxvii, figs. 3-15. 



1872. Dioraniscus, Meek. American Journal of Science, Third Ser., vol. iv, p. 280. 



1873. Triplesia, Meek. Geological Survey Ohio ; Palaeontology, vol. i, pp. 176-179, pi. xv, fig.s. la-k. 

 1877. Triplesia, Whitfield. Ann. Rept. Geol. Survey of Wisconsin, p. 51. 



1882. Triplesia, Whitfield. Geology of Wisconsin, vol. iv, j). 172, pi. x, figs. 1, 2. 



1883. Triplesia, Davidson. British Silurian Brachiopoda. Suppl., pp. 141-147. 

 (?) 1884. Triplesia, Walcott. Palseontology Eui'eka District, p. 75, pi. xi, figs. 7, 8. 



1889. Triplesia, Whitfield. Bull. American Museum Nat. Hist., vol. ii, No. 2, p. 43, pi. vii, figs. 5-8. 

 Compare Strtptis, Davidson. Geological Magazine, vol. viii, p, 150, pi. v, fig. 13. 1881 ; and Bi'itish 



Silurian Brachiopoda. Suppl., p. 139. 



Diagnosis. Shell trilobate, transverse, unequally biconvex. Hinge-line 

 straight and quite short. Pedicle-valve shallow, convex about the beak, but 

 depressed anteriorly by a broad and deep median sinus ; cardinal area low, 

 erect and well defined ; delthyrium covered by a narrow, convex plate, with a 

 circular foramen at the apex. In the interior the teeth are well developed and 

 supported by short dental lamellse longitudinally dividing the umbonal cavity 

 near its apex. Muscular area small, comprising two lateral scars, separated by 

 a longer central adductor impression. The brachial valve is very convex, and 

 bears a strong median fold. The cardinal area is very narrow and the beak 

 closely incurved. In the interior is an erect cardinal process, which is deeply 



* The derivation of the term "Triplesia," as it is currently written, was given in the original descrip- 

 tion as from TptTrAaCTtoj" = triplasius. The correct form of the word, therefore, would have been Triplasia, 

 but this term apjiears to have been already in use. Dr. CEhlert has suggested the change to Triplecia, 

 which involves a derivation from a diiferent root, TpnrXeKng- = tri])lex. 



