198 PALEONTOLOGY OF NEW YORK. 



HEBERTELL A 



(nom. propos). 



V. Group of Orthis sinoata, Hall. 



PLATE VA, FIGS. 1-13. 



1843. Orthis, Conrad. Proc. Acad. Nat. Sci. Phi la , vol. i, p. 333. 



1847. Ortliis, Hall. Palaeontology of N. Y., vol. i, pp. 118, 125-128, pi. xxxii, fig.s. 3, 12 ; pi. xxxiia, fig. 



2 and pi. xxxiib, figs. 1, 2. 



18i)9. Orthis, Billings. Canadian Nat. and Geol., vol. iv, pp. 435, 436, figs. 11-14. 



1862. Orthis, Billings. Palieozoic Fossils, vol. i, p. 137, fig. 114. 



1863. Ortfti?, Billings. Geology of Canada,. p. 129, figs. 55, 56 ; p. 167, figs. 148, 150 and p. 210, fig. 210. 

 1873. Orthis, Mbbk. Palseontology Ohio, vol. i, pp. 96, 99, 101, pi. viii, fig. 4, and pi. ix, figs. 1-3. 

 1875. Orthis, Mii.ler. Cincinnati Quart. Jour. Sci., vol. ii, pp. 28, 34, 36, 40. 



1875. Orthis, White. Geogr. and Geol. Expl. west 100th Merid. p. 70, pi. iv, fig. 11. 



1881. Orthis, White. Tenth Ann. Rept. Indiana State Geol., p. 117, pi. ii, figs. 10-12. 



1882. Orthis, Whitfield. Geology of Wisconsin, vol. iv, p. 260, jil. xii, figs. 17, IS. 



1882. Orthis, Miller. Journ. Cincinnati Soc. Nat. Hist., vol. v, p. 40, pi. i, fig. 5. 



1883. Orthis, Hall. Rept. N. Y. State Geologist for 1882. pi. xxxiv, tigs. 31-34; pi. xxxv, figs. 16-22. 



1884. Ortlm, Walcott. Palseontology Eureka District, p. 74, pi. xi, fig. 6. 



1885. Orthis, Foerstb. Bull. Denison Univei-sity, vol. i, pp. 85, 87, pi. xiii, figs. 13, 15, 16, 20, 21. 

 1887. Orthis, Shalbr. Memoirs Kentucky Geol. Survey, plate viii. 



1889. Orthis, Nbttleroth. Kentucky Fossil Shells, p. 86, pi. xxxiv, figs. 14-20. 



This division is distinguished both by its external and internal characters ; 

 the pedicle-valve has a well developed, often much elevated cardinal area and 

 a long, straight hinge-line ; its surface is depressed-convex, always less convex 

 than the opposite valve which is frequently gibbous or inflated. The surface 

 is covered with a great number of fine, rounded, closely crowded plications 

 which increase rapidly by intercalation, and are crossed by lamellose growth- 

 lines, and fine concentric striae. On the interior of the pedicle-valve the teeth 

 are large and .supported by thick lamellae which are continued as a strong ridge 

 around a short, obcordate muscular area. This area is medially divided by a 

 prominent ridge upon the summit of which lies the linear scar of the adduc- 

 tors. The flabellate lateral impressions are sometimes divisible into their two 

 components, diductors and adjustors, and in old individuals the impression of 

 the pedicle-muscle is often distinct. 



In the brachial valve the dental sockets are narrow and are enclosed 

 beneath and on the inner side by the strong crural plates. The cardinal 

 process is elongate and simple, sometimes thickened, often crenulate, but not 

 lobed at its posterior extremity. This process unites with tlie inner bases of 



