268 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



In ophiurids the oral skeleton, or syngnaths, is composed of three 

 pairs of adambulacrals and ambulacrals. Of these the two first 

 pairs alone are prominent and preserved. The third pair remains 

 internal, small, and rudimentary. 



Family ONYCHASTERID^ Miller. 



Onychasteridae MILLER, N. Amer. Geol. Pal., 1889, p. 216. GREGORY, Proc. Zool. 

 Soc. London for 1896, 1897, p. 1040. STURTZ, Verh. iiaturh. Ver. preuss. 

 Kheinl., etc., vol. 56, 1900, p. 202. SCHONDORF, Jahrb. nassauisch. Ver. 

 Naturk., Wiesbaden, vol. 63, 1910, p. 235. 



Original diagnosis. " Strep tophiurse with well-developed vertebral 

 ossicles, and with very flexible, contorted, unbranched arms; there 



U.S. " 



u. ^ 



FIGS. 35 AND 36. VERTEBRAL OSSICLE OF OPHIURA CILIARIS. AFTER MULLER FROM GREGORY. 35; 

 ABORAL SURFACE; 36, ADORAL SURFACE, c, CANAL FOR THE PODION (SHOWN BY REMOVAL OF A PART OF 



MUSCLE FIELD ON RIGHT SIDE); J.W., LOWER MUSCLE FIELD; l.f., LOWER AND ./., UPPER CANAL FURROWS, 

 ., UMBO; U. *., UMBONAL SOCKET. 



are no external arm plates, the integument containing granules 

 only.' 7 



Contains the genus : 



Ony chaster Meek and Worthen. 



Genus ONYCHASTER Meek and Worthen. 



Onychaster MEEK and WORTHEN, Geol. Surv. Illinois, vol. 3, 1868, p. 526; Proc. 

 Acad. Nat. Sci. Philadelphia, vol. 21, 1869, p. 82; Geol. Surv. Illinois, vol. 5, 

 1873, p. 474. ZITTEL, Handb. Pal., vol. 1, 1879, p. 443. MILLER, N. Amer. 

 Geol. Pal., 1889, p. 264. STURTZ, Verh. naturh. Ver. preuss. Rheinl., etc., 

 vol. 50, 1893, p. 30. GREGORY, Proc. Zool. Soc. London for 1896, 1897, p. 

 1040. STURTZ, Verh. naturh. Ver. preuss. Rheinl., etc., vol. 56, 1900, p. 183. 

 SCHONDORF, Jahrb. nassauisch. Ver. Naturk., Wiesbaden, vol. 62, 1909, 

 pp. 47-61, vol. 63, 1910, p. 240; Palaeontographica, vol. 57, 1910, p. 59. 

 SPENCER, Mon. Brit. Pal. Asterozoa, pt. 1 (Palseontogr. Soc. for 1913), 1914, 

 pp. 26, 50. I. B. J. SOLLAS, Philos. Trans. Hoy. Soc. London, ser. B, vol. 

 204, 1913, p. 51. SCHONDORF, Jahrb. nassauisch. Ver. Naturk., Wiesbaden, 

 vol. 66, 1913, pp. 97-114. 



