KEVISION OF PALEOZOIC STELLEKOIDEA. 215 



The Auluroidea can be divided into two orders on the basis of 

 whether the ambulacrals on each side of the median line are arranged 

 alternately (the Lysophiurae), or are opposite to one another (the 

 Streptophiurae). The following classification is a modification of 

 the one offered by Gregory in 1897, and kis work was in turn a 

 modification of that of Bell in 1892. 



After the present work was written, its author first became aware 

 of the works of Sollas and Sollas, and Spencer. The reader should 

 consult those papers for important studies on the Auluroidea. 



Order LYSOPHIUR^E: Gregory. 



Encrinasterise BRONN (part), Klassen u. Ordnungen d. Tierreichs, vol. 1, 1859, 



p. 287. SCHONDORF, Palaeontographica, vol. 57, 1910, p. 61. 

 Ophio-Encrinasterise STURTZ, Verb, naturh. Ver. preuss. Rheinl., etc., vol. 56, 



1900, p. 198. SCHONDORF, Jahrb. nassauisch. Ver. Naturk., Wiesbaden, 



vol. 63, 1910, pp. 234, 237. 

 Lysophiurse GREGORY, Proc. Zool. Soc. London for 1896, 1897, p. 1030 (contains 



Protasteridse and Palaeophiuridae) ; Treat. Zool., vol. 3, Echinoderma, 1900, 



p. 274. SOLLAS and SOLLAS, Philos. Trans. Roy. Soc. London, ser. B, vol. 



202, 1912, p. 223. 

 Ophiurasterix SCHONDORF, Jahrb. nassauisch. Ver. Naturk., Wiesbaden, vol. 63, 



1910, p. 251. 



Auluroidea in which the ambulacral ossicles of adjoining columns 

 are alternate to one another. The individual plates are separate and 

 not coossified into vertebrae. 



Remarks. The Lysophiurae are Paleozoic or primitive Auluroidea, 

 that is, ophiurid-like animals, with wide and open ambulacral furrows 

 in which the ambulacralia are free and alternately arranged. The 

 ambulacralia are common to the actinal and abactinal sides. 

 This order contains the following families: 



Protasteridse. Have boot-shaped ambulacralia ventrally. 

 Palseophiuridae. Have subquadrate ambulacralia ventrally. 

 Encrinasteridae. Have boot-shaped ambulacralia ventrally 

 and large disks that are bordered by marginalia. 



Family PROTASTERIDSE Miller. 



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

 Soc. London for 1896, 1897, p. 1031; Treat. Zool., vol. 3, Echinoderma, 1900, 

 p. 274. PARKS, Trans. Canadian Inst., vol. 8, 1908, p. 366. 



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

 p. 202. 



"Lysophiurae with boot-shaped ambulacral ossicles, each composed 

 of a 'body ' in the median line of the arm, and a lateral 'wing' at right 

 angles to it" (Gregory). There is either a well-marked scale-covered 

 or granular disk, and five flexible arms. The adambulacral plates are 

 rather stout, with many lateral spines. 



