446 A. Olsson — New Genus of Palceechinoidea. 



Perischodomus biserialis McCoy 



" illinoisensis Worthen & Muller Chester lime- 



stone — Pope Co. 111. 

 Lepidechinas varispinus Hall, Chemung Penn. and Wav- 

 erly — groups of Ohio 

 " imbricatus Hall, Burlington limestone — Bur- 



lington Ohio 

 Lepidechinoides ithaceusis Ithaca beds Portage formation 

 N. Y. 



The type specimen herein described was found at the Uni- 

 versity quarry, sometimes called the McCormick quarry, near 

 the lower border of the Cornell campus. This quarry is situ- 

 ated in the zone* characterized by the presence of Spirifer 

 mesastriaiis and Cryjptonella eudora, which in the Ithaca 

 region are rarely found above or below these beds. This zone 

 is confined to about twenty -five feet in the center of the Ithaca 

 shale member and of which fifteen feet are exposed in this 

 quarry. It is made up of hard sandstone layers with few shale 

 beds. Fossiliferous layers sometimes occur so thickly filled 

 with fossils as to produce an impure siliceous limestone. On 

 passing eastward this zone is believed to thicken and to be 

 represented in the Chenango valley by the Oneonta sandstone, 

 which there overlies the Ithaca. Besides Spirifer mesa- 

 striaiis and Cryjptonella eudora, the following fossils are 

 quite characteristic of this zone : Actinopteria boydi / Cawia- 

 rotoechia eximia / Leiorliynchus mesacostale • Orthoeeras 

 bebryx • Gomjihoceras tumidum and Stictapora meeki asso- 

 ciated with numerous crinxfid stems. 



Those who desire a more detailed comparison of the genus 

 herein described with the other genera in the family will find 

 the works listed below to be of service : 



Hall. Desc. New Spec. Crin., 1861, p. 18. 



Hall. 20th Rep. N. Y. State Cab. Nat. Hist., 1868, p. 340, 



pi. 9, fig. 10. 

 Keeping, W*. Notes on the Paleozoic Echini, Quart. Jour. 



Geol. Soc, London, vol. xxxii, p. 35, 1876. 

 Worthen & Miller. Geol. Surv. Ill, vol. vii, 1883, p. 333, 



pi. 31, fig. 8. 

 Jackson, R. T. Bull. Geol. Soc. Am., vol. vii, 1896, p. 222-242. 

 Klem, M. J. A Revision of the Paleozoic Palgeechinoidea 



with complete bibliography. St. Louis Acad. Science 



Trans., vol. xiv, 1904, pp. 1-98, 6 pi. 



Ithaca, N. Y. 

 Jan. 4, 1912. 



*Bull. U. S. G. S., No. 3, p. 17. Watkins Glen-Catatonk folio, U. S. G. S., 

 No. 169, field edition, pp. 64, 65, 92, library edition, pp. 6, 8, 12. 



