Klem — Revision of the Palaeozoic Palae'echinoidea. 13 



1881. Palaeodiscus ferox. Neumayr, Sitzb. K. Akad. Wiss. 



Wien, Bd. 84, Abth. 1, p. 155, taf. 1, fio-. 8. 

 1897. Palaeodiscus ferox. Gregory, Quart. Journ. Geol. 



Soc. London, vol. 53, pt. 1, p. 129, pi. 7, fig. 5. 

 1899. Palaeodiscus ferox. Sollas, Quart. Journ. Geol. Soc. 



London, vol. 55, pt. 4, p. 701, figs. 6-11. 

 Body composed of large plates furnished with spines. 

 Seven or eight columns in each interambulacrum. Ambulacra 

 composed of long, thin plates in two rows. Powerful teeth 

 known. 



Geological formation and locality : Lower Ludlow, Leint- 

 wardine Flags. 



II. EcHiNOCYSTiDAE Gregory 1897.* 



Body spherical. Ambulacral plates perforated by a pore pair 

 each. Pore pairs biserial. Most of the plates low primaries, 

 but demi-plates occur. Mouth central, anus excentric, opening 

 in posterior interambulacrum and protected by a group of 

 large plates. Apical plates absent. Jaws large and powerful. 



a. EcHiNOCYSTis Thomson 1861. f 



Syn. Cystocidaris Zittel 1879. J 



Body spheroidal, test thin and flexible. Ambulacra consist 

 of four columns of small, simple, demi-plates with biserial 

 pore pairs. The interambulacra consist of ten columns each 

 usually of numerous, irregular, angular plates, most of which 

 bear small granules, supporting short, sharp, movable spines. 



1. EcHiNOCYSTis POMUM Thomson. 



1861. Echinocystis pomum. Thomson, Edin. New. Phil. 



Journ., n. s. vol. 13, p. 106, pi. 3, 4. 

 1861. Echinocystis uv a . Thomson, Edin, New Phil. Journ., 



n. s. vol. 13, p. 106, pi. 4. 



♦ Quart. Journ. Geol. Soc. London, vol. 53, pt. 1, p. 133. 

 t Edin. New Phil. Journ., n. s. vol. 13, p. lOG. 

 X Handbuch der Palaeontologie Bd. 1, p. 480. 



