RRACHIOPODA. 269 



Genus TRIPLEGIA* Hall. 1858. 



PLATE XI c, FIGS. 1-22. 



1S42. Terebratula, von Eichwald. Urwelt Russlands, vol. ii, p. 49, plati; ii, figs. 6 a, !>, e. 



1842. Atrypa, Emmons. Geology of N. Y. ; Kept. Second District, p. 395, fig. 6. 



184."). iSpirifer, de Verneuil. Geol. Russ. et des Mont, de rOural, p. 149, pi. viii, fig. 7. 



1846. Orthis, Producta, McCoy. Synopsis Siliii-ian Fo.ss. Ireland, p. 25, pi. iii, fig. 8; p. SO, pi. iii, Hg. 12. 



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



1848. Orthis, Phillips and Saltbk. Mem. Geol. Surv. United Kingdom, vol. ii, p. 289. 

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



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



1859. iSpirifer, von Eichwald. Lethiea Rossici, vol. i, p. 697. 



1859. T^iptesia, Hall. Palaeontology of N. Y., vol. iii, pp. 522, 523, figs. 1-3. 



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



(?) 1863. Camarella, Billings. Geology of Canada, p. 231, fig. 247. 



(1) 1865. Camardla, Billings. Palaeozoic Fossils, vol. i, p. 220. 



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



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



pi. XXV, figs. 3-5. 



1871. Orthis, Davidson. Bi-itish Silurian Bi-achiopoda, p. 273, pi. xxxvii, figs. 3-15. 



1872. Dlci'aniscus, Meek. American Journal of Science, Third Ser., vol. iv, p. 280. 



1873. Triplesia, Meek. Geological Survey Ohio; Palaeontology, vol. i, pp. 176-179, i>\. xv, figs. la-k. 

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



1882. Triplesia, 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 Eui'eka District, p. 75, pi. xi, figs. 7, 8. 



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

 Compare *S<repfi«, Davidson. Geological Magazine, vol. viii, p 150, jil. v, fig. 13. 1881 ; and Br-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 lamellaB 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 TplTrXdaiog- = triplasiris. The correct form of the word, therefore, would have been Tbiplasia, 

 but this term appears to have been already in use. Dr. (Ehlert has suggesteil the change to Triplegia, 

 which involves a derivation from a different root, rpiirXeKiig- ^ triplex. 



