BRACHIOPODA. 285 



1871. Strophomena, Kayser. Zeitschrift der deutsch. fjeolog-. Gesellschaft, vol. xxiii, pp. t!20, 621,624, 



625, 627, 630, pi. xiv, fi!,'s. 4, 5. 



1872. Strophomena, Barrandb. Syst^me SiUirien du Centre de la Boheme, pi. xl, t\gn. 10-19 ; iil. xlii, 



H^s. 6-14, 21-28 ; pi. xliii, figs. 1-5, 17-29 ; pi. xliv, Hg-s. 1-30. 



1873. Strophodmita, Hall ami Whitfield. Twenty-third Rept. N. Y. State Cab. Nat. Hist., pi). 236, 



239, pi. xi, figs. 8-11. 



1873. 8trophodo7ita, Nicholson. Rept. Palseontology Pi'ovince of Ont:ii-io, pp. (i4, 65, 67. 



1874. Strophomena, Billing.s. Palaeozoic- Fossils, vol, ii, pp. 20, 24, 26-29. 



1877. Strophodonta, Hall and Whitfield. King's Expl. and Siirv. Fortieth Parallel, vol. iv, p. 246, 



pi. iii, figs. 1-3. 



1878. Stropliodonta, Calvin. Bulletin No. 3, United States Geological Survey, vol. iv, pp. 727, 728. 



1878. iStrop/iodoiita, Barrett. American Journal of Science vol. xv, p. 372. 



1879. Straphodonta, Hall. Twenty-eighth Rept. N.Y. State Mus. Nat. Hist., p. 151, pi. xxiii, figs. 9, 10. 



1880. Strophomena, Dawson. Canadian Natui'alist and Geologist, 2nd Ser.. vol. ix, p. 341. 



1881. Strophodouta, White. Tenth Rept. Indiana State Geologist, p. 132, pi. iv, figs. 6, 7. 



1881. Strophomena, Davidson. Brachiopoda Bndleigh-Salterton Pebble-bed, pp. 348-351, pi. xxxix, 



tigs. 1, 2, 4-11. 



1882. Strophodonta, Hall. Eleventh Ann. Rept. State Geologist Indiana, p. 289, pi. xxiii, figs. 9, 10; 



pi. xxvii, fig. 18. 



1882. Strophodonta, Whitfield. Geology of Wisconsin, vol. iv, p. 327, pi. xxv, fig. 18. 



1883. Strophodonta. Hall. Ann. Rept. N. Y. State Geologist for 1882, i>ls. xiii (44) ; xiv (45) ; xv (46), 



figs. 1-24. 



1884. Strophodonta, Walcott. Palseontology Eureka Dist., pp. 118-122, pis. ii, xi, xiii. 

 1889. StrophodAmta, Nettelrotii. Kentucky Fossil Shells, pp. 142-150. 



1889. Strophomena, Barrois. Faune du Calcaire d'Erbray, pp. 63-65, 67, pi. iv, figs. 6, 8-10. 



Diagnosis. Shells normally concavo-convex or subplano-convex. Cardinal 

 area common to the two valves, that of the brachial valve narrower or linear ; 

 smooth or finely striated longitudinally, sometimes showing through the outer 

 laminae of the shell strong, parallel, transverse bars, which project beyond the 

 cardinal margin as short processes, and articulate with a corresponding series 

 of pits in the opposite valve. The earliest species have these denticulations 

 developed only for a short distance on each side of the center, while in the lat- 

 ter faunas they extend the entire length of the hinge-line. In the type-species 

 the delthyrium is usually completely closed by the extension of the shelly laminiB 

 of the area, and on the inside by the formation of a callosity between the 

 apophyses of the cardinal process. Sometimes a low, narrow, convex deltidium 

 is present, but in the early species the delthyrium is frequently open. 



From the normal position of the dental laraellse there extend two diverging, 

 sometimes nearly vertical, ridges of variable strength, bounding the post-lateral 

 portion of the muscular area, which is not limited by a ridge in front. The 

 entire muscular area consists of two broad fiabelliform diductor scars, enclosing 

 an oval adductor which is distinctly divided into anterior and posterior ele- 



