BRACHIOPODA. 269 



Genus TRIPLEGIA,* Hall. 1858. 



PLATE XI 0, FIGS. 1-22. 



1842. Terebratuki, von Eichwat.ii. Ui-welt Russlamls, vul. ii, p. 4i1. plate ii, fig's. G a, b, c. 



1842. Atrypa, Emmons. GiMilogy of N. Y. ; Rept. .S(m'oiu1 Disl,i-i<-t, ji. iiDfi, fiff. 6. 



1845. Spirifer, de Vernbiui,. Geol. Russ. et iJes Moiit. df r()iii:il. p. M'.i, pi. viii, fig-. 7. 



1846. Orthis. Producta, McCoy. Synopsis Siluri;ui Fo.ss. li-dliiinl, p. 2;"), pi. iii, i\g. 3; p. 30, jil. iii, liy. 12. 



1847. Atrypa, Hall. PaliBOutology of N. Y., vol. i, jip. 137, 13il, pi. xxxiii, fig-s. 1,2; pi. xxxiii*, ^g. I. 



1848. Orthis, Phillips and Salter. Mem. Geol. Sm-v. United Kin^jdom, vol. ii. p. 2.S9. 

 1852. Hemithyris, McCoy. Biitish Paleozoic Fo.ssils, p. 201. 



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



1859. Spirifcr, von Eichwald. Lethaea Ro.ssiea, vol. i, p. 697. 



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



(1) 1861. Camarella, Billings. Canadian Naturalist and Geologist, vol. vi, p. 318, tig. 3. 



(1) 1863. Cmmrella, Billings. Geology of Canada, p. 231, fig. 247. 



0) 1865. Camarella, Billings. Palseozoic Fossils, vol. i, p. 220. 



1866. Orthis, Salter. Mem. Geol. Surv. United Kingdom, vol. iii, |i. ()97. 



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



pi. XXV, figs. 3-5. 



1871. Orthis, Davidson. Bi'itish Silurian Brachiopoda, p. 273, jil. xxxvii, tigs. 3-15. 



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



1873. Triplesia, Meek. Geological Survey Ohio ; Palajontology, vol. i, p)i. 17(i 179, pi. x\-. lij^s. I a-k. 

 1877. Triplesia, Whitfield. Ann. Re])t. Geol. Survey of Wisconsin, ]>. 51 



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



1883. Triplesia, Davidson. British Silurian Brachiopoila. Sujipl., pji. 141-147. 

 (?) 1884. Triplesia, Walcott. Palsontolog-y Eureka 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 Strcptis, Davidson. Geological Magazine, vol. viii, p 150, pi. v, tig. 13. 1881 ; and Briti.sh 



Silurian Brachiopoda. Sn]i))l., 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 lainellse 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 TpiTrXdaiog- = triplasius. The correct form of the word, therefore, woidd have been Tripi.asia, 

 but this term appears to have been already in use. Dr. CEhlert has suggested the <-hange to Thh'I.kiia, 

 which involves a derivation from a different root, rfjnTXsK/'i^'= triplex. 



