246 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



Order STREPTOPHIUR^ Bell. 



Streptophiurse BELL, Proc. Zool. Soc. London for 1891, 1892, p. 179. GREGORY, 



Proc. Zool. Soc. London for 1896, 1897, p. 1036; Treat. Zool., vol. 3, Echino- 



derma, 1900, p. 274. 

 Protophiurex STURTZ, Verh. naturh. Ver. preuss. Rheinl., etc., vol. 56, 1900, 



p. 200. SCHONDORF, Jahrb. nassauisch. Ver. Naturk., Wiesbaden, vol. 63, 



1910, pp. 234, 239, 251. 

 Ophiurasterise SCHONDORF, Palseontographica, vol. 57, 1910, p. 61. 



Diagnosis by Gregory (1897). Auluroidea "in which the ambu- 

 lacral ossicles are opposite and are generally fus.ed into vertebral 

 ossicles. In such cases the vertebral ossicles articulate by a more 

 or less simple ball-and-socket joint." 



"Remarks. The main character of this order is that the ambu- 

 lacral ossicles are paired, but primitive. The order differs from the 

 preceding [Lysophiurse] by having the vertebral ossicles always 

 opposite instead of alternate. In some of the simplest members of 

 the order, as Ophiurina, the ossicles are not fused, there are no 

 ventral arm shields, and an ambulacral furrow runs along the ven- 

 tral side of the arm. In the next higher family, as in the genus 

 Lapworihura, the ambulacral ossicles are fused, but have plain 

 articulating surfaces, and there is* an ambulacral furrow." 

 Contains the f amilies : 



Ophiurinidae. 



Lapworthuridas. 



Eoluidiidae. 



Aganasteridae. 



Cholasteridae. 



Family OPHIUKINIIXE Gregory. 



Ophiurinidse GREGORY, Proc. Zool. Soc. London for 1896, 1897, p. 1037; Treat. 

 Zool., vol. 3, Echinoderma, 1900, p. 275. STURTZ, Verh. naturh. Ver. preuss. 

 Bheinl., etc., vol. 56, 1900, p. 201. SCHONDORF, Jahrb. nassauisch. Ver. 

 Naturk., Wiesbaden, vol. 63, 1910, p. 234. 



Original diagnosis. " Strep tophiurae with ambulacral ossicles, 

 only slightly united, and without ventral arm plates." 

 Contains the genera: 

 Ophiurina Sttirtz. 

 Tremataster Worthen and Miller. 



Genus OPHIURINA Sturtz. 



Ophiurina STURTZ, Palaeontographica, vol. 36, 1890, p. 232. GREGORY, Proc. 

 Zool. Soc. London for 1896, 1897, p. 1037. 



Gregory's diagnosis reads as follows: "Disk circular, with mar- 

 ginal plates. Ambulacral ossicles long, narrow bars. Syngnaths 

 rod-shaped. Adambulacral plates absent or altogether lost from 

 the fossil." 



