BRACHIOPODA. 
43 
become obliterated by subsequent overgrowth, but this assumption has yet to 
be verified. That maturity induces a modification of the deltidium is evinced 
by the internal median thickening of this plate in C. alta. 
1852. 
1855. 
18.57. 
1858. 
1858. 
1859. 
1860. 
1861. 
1862. 
1863. 
1863. 
1867. 
1867. 
1868. 
1868. 
187.3. 
1874. 
1874. 
1875. 
1884. 
1888. 
1889. 
1889. 
Genus CYRTINA, Davidson. 1858. 
PLATES XXVII, XXXIX. 
Spirife)', Hall. Palseontology of N. Y., vol. ii, p. 266, pi. liv, fig. 7. 
Cyrtia, Shomard. Geology of Missouri, p. 204, pi. c, fig. 3. 
Cyrtina, Hall. Tenth Rept. N. Y. State Cab. Nat. Hist., pp. 64, 165, 166. 
Cyrtia, Hall. Geology of Iowa, vol. i, pt. ii, p. 612, pi. v, fig. 2. 
Cyrtina, Davidson. Monogr. British Carboniferous Brachiopoda, p. 66. 
Cyrtia, Hall. Palseontology of N. Y., vol. iii, pp. 206,429, pi. xxiv, fig. 1; pi. xcvi, figs. 1-6; 
pi. xcviii, fig. 8, 
Cyrtia, Swallow. Trans. St. Louis Acad. Sci., vol. i, pp. 647, 648. 
Cyrtia, Billings. Canadian Journal, vol. vi, new ser., p. 262, figs. 80-82; p. 263. 
Cyrtia, White. Proc. Boston Soc. Nat. Hist., vol. ix, p. 25. 
Cyrtia, Billings. Canadian Naturalist and Geologist, vol. viii, p. 37. 
Cyrtia, Billings. Geology of Canada, p. 384, fig. 415. 
Cyrtina, Hall. Twentieth Rept. N. Y. State Cab. Nat. Hist., p. 261. 
Cyrtina, Hall. Palseontology of N. Y., vol. iv, pp. 263-270, pi. xliv, figs. 26-55. 
Cyrtina, Meek and Worthen. Geol. Survey of Illinois, vol. iii, jip. 383, 436, pi. vii, fig. 3; 
111. xiii, fig. 4. 
Cyrtina, Meek. Trans. Chicago Acad. Sci., vol. i, pp. 97, 99, 100, pi. xiv, figs. 5-7, 8, 10. 
Cyrtina, Nicholson. Palieontology Province of Ontario, p. 83. 
Cyrtina, Billings. Palaeozoic Fossils, vol. ii, p. 49, pi. 3a, fig. 6. 
Cyrtina (t), Rathbdn. Bull. Buffalo Soc. Nat. Science, vol. i, p. 242. 
Cyrtina, Hall and Whitfield. Twenty-seventh Rept. N. Y. State Mus. Nat. History, pi. ix, 
figs. 14-16. 
Cyrtina, Walcott. Monogr. U. S. Geol. Survey, vol. viii, pp. 146, 147, pi. iii, fig. 2. 
Cyrtina, Herrick. Bulletin Denison University, vol. iv, p. 14. 
Cyrtina, Nettelroth. Kentucky Fossil Shells, pp. 95, 96, pi. xiii, figs. 4-16, 21-24. 
Cyrtina, Simpson. Trans. American Philosophical Society, p. 439. fig. 4. 
Diagnosis. Shells usually of small size and semipyramidal contour. Pedicle- 
valve with a high, vertical or arched cardinal area, which may be unsymmetrical 
from distortion or unequal lateral growth; this area is divided medially by an 
elongate-convex deltidium, which may be perforated at any point below the 
apex, by a circular, direct or oblique foramen, or be without any evidence of 
such foramen. When present the foramen is accompanied by a sinus on the 
deltidium, extending from it to the apex of the valve; even when this foramen 
has been closed from senile deposition of testaceous matter this foraminal 
groove may remain. 
