BRA CHIOP ODA. 
269 
Genus TRIPLECIA* Hall. 1858. 
PLATE XIC, PIGS. 1-22. 
1842. Terebratula, von 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, fig. 6. 
1845. iSpirifer, de Verneuil. Geol. Russ, et des Mont, de j’Oural, p. 149, pi. viii, fig. 7. 
1846. Orthis, Producta, McCoy. Synopsis Silurian Foss. Ireland, p. 25, pi. iii, fig. 3; p. 30, pi. iii, fig. 12. 
1847. Atrypa, Hall. Palaeontology of N. Y., vol. i, pp. 137, 139, pi. xxxiii, figs. 1, 2 ; pi. xxxiii*, fig. 1. 
1848. Orthis, Phillips and Salter. Mem. Geol. Surv. United Kingdom, vol. ii, p. 289. 
1852. Hemithyns, McCoy. British Palaeozoic Fossils, p. 201. 
1858. Tnplesia, Hall. Twelfth Rept. N. Y. State Cab. Nat. Hist., p. 44, figs. 1-3. 
1859. tSpirife)', von Eichwald. Lethaea Rossica, vol. i, p. 697. 
1859. Triplesia, Hall. Palaeontology of N. Y., vol. iii, pp. 522, 523, figs. 1-3. 
(?) 1861. Camarella, Billings. Canadian Naturalist and Geologist, vol. vi, p. 318, fig. 3. 
(?) 1863. Camarella, Billings. Geology of Canada, p. 231, fig. 247. 
(?) 1865. Camarella, Billings. Palaeozoic Fossils, vol. i, p. 220. 
1866. Orthis, Salter. Mem. Geol. Surv. United Kingdom, vol. iii, p. 697. 
1869. Tnplesia, 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. Dicraniscus, Meek. American Journal of Science, Third Ser., vol. iv, p. 280. 
1873. Tnplesia, Meek. Geological Survey Ohio ; Palaeontology, vol. i, pp. 176-179, pi. xv, figs. 1 a-k. 
1877. Triplesia, Whitfield. Ann. Rept. Geol. Survey of Wisconsin, p. 51. 
1882. Tnplesia, Whitfield. Geology of Wisconsin, vol. iv, p. 172, pi. x, figs. 1, 2. 
1883. Triplesia, Davidson. British Silurian Brachiopoda. Suppl., pp. 141-147. 
(?) 1884. Triplesia, Walcott. Palaeontology Eureka District, p. 75, pi. xi, figs. 7, 8. 
1889. Tt'iplesia, Whitfield. Bull. American Museum Nat. Hist., vol. ii, No. 2, p. 43, pi. vii, figs. 5-8. 
Compare Streptis, Davidson. Geological Magazine, vol. viii, p 150, pi. v, fig. 13. 1881; and British 
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 lamellae 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 TpnrXdaiog’ = tnplasius. The correct form of the word, therefore, would have been Triplasia, 
but this term appears to have been already in use. Dr. (Ehlert has suggested the change to Triplecia, 
which involves a derivation from a different root, TpnrXeiirjg- — triplex. 
