BRACHIOPODA. 
285 
1871. '^Strophomena, Kayser. Zeitschrift der deutsch. geolog. Gesellschaft, vol. xxiii, pp. 620, 621,624, 
625, 627, 630, pi. xiv, figs. 4, 5. 
1872. Strophomena, Barrande. Systeme Silurien du Centre de la Boheme, pi. xl, figs. 10-19 ; pi. xlii, 
figs. 6-14, 21-28 ; pi. xliii, figs. 1-5, 17-29 ; pi. xliv, figs. 1-30. 
1873. Strophodonta, Hall and Whitfield. Twenty-third Rept. N. Y. State Cab. Nat. Hist., pp. 236, 
239, pi. xi, figs. 8-11. 
1873. Strophodonta, Nicholson. Rept. Palaeontology Province of Ontario, pp. 64, 65, 67. 
1874. Strophomena, Billings. Palaeozoic Fossils, vol. ii, pp. 20, 24, 26-29. 
1877. Strophodonta, Hall and Whitfield. King’s Expl. and Surv. Fortieth Parallel, vol. iv, p. 246, 
pi. iii, figs. 1-3. 
1878. Strophodonta, Calvin. Bulletin No. 3, United States Geological Survey, vol. iv, pp. 727, 728. 
1878. Strophodonta, Barrett. American Journal of Science vol. xv, p. 372. 
1879. Strophodonta, Hall. Twenty-eighth Rept. N.Y. State Mus. Nat. Hist., p. 151, pi. xxiii, figs. 9,10. 
1880. Strophomena, Dawson. Canadian Naturalist and Geologist, 2nd Ser.. vol. ix, p. 341. 
1881. Strophodonta, White. Tenth Rept. Indiana State Geologist, p. 132, pi. iv, figs. 6, 7. 
1881. Strophomena, Davidson. Brachiopoda Budleigh-Salterton Pebble-bed, pp. 348-351, pi. xxxix, 
figs. 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, pis. xiii (44); xiv (45) ; xv (46), 
figs. 1-24. 
1884. Strophodonta, Walcott. Palaeontology Eureka Dist., pp. 118-122, pis. ii, xi, xiii. 
1889. Strophodonta, Nettelroth. 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 laminae 
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 lamellae 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 flabelliform diductor scars, enclosing 
an oval adductor which is distinctly divided into anterior and posterior ele- 
