300 



ECHINODERMATA— ECHINOZOA 



PHYLÜM IV 



Family 1. Archaeocidaridae M'Coy. 



Two columns of plates in an ambulacral area. Four to eight columns of plates 

 in an interambulacral area, imbricating . Primordial and additional interambulacral 

 plates are resorhed in the advance of peristome. Oculars, genitals and periproä 

 imperfeäly known. Peristome with many rows of ambulacral and interradial non- 

 ambidacral plates. Spines large primaries with perforate tubercles in the cenire of 

 each inferambidacral plate, also secondary spines and imperforate tubercles. Devonian 

 to Permian. 



Eocidaris Desor. Known from fragmentary interambulacral plates and 

 spines, primary tubercles of plates without a basal terrace. Only one species 

 is recognised, E. laevispina (Sandb.). Devonian; Germany. 



Archaeocidaris M'Coy. Ambulacral plates all alike, of equal height. Four 

 columns of plates in an interambulacral area. Primary spines large, tapering 

 or inflated, smooth or with lateral spinules. Primary tubercles with basal 

 terrace and scrobicular ring. Many species fragmentarily known. The most 

 completely known are A. wortheni Hall (Figs. 366, e; 371, Cy 427, Ä-C\ 

 A. rossica (Buch), A. urii (Flem.). Lower Carboniferous and Carboniferous ; 

 Europe and North America. Permian ; North America and India. 



Fio. 427. 



Archaeocidaris wortheni Hall. Lower Carboniferous; Burlington, Iowa. A, Portion of ventral rogion, 

 showing jaws, i/i., B, An lArab plate viewed from above and from the side. C, Portion of Amh, enlarged. 

 D, Spina of A. keokuk Hall. Lower Carboniferous ; Warsaw, Illinois (after Hall), 



Lepidocidaris Meek and Worthen. Ambulacral plates low, with also higher, 

 wider and wedge-shaped plates. Six to eight columns of plates in an inter- 

 ambulacral area. Primary spines cylindrical. Primary tubercles with no 

 basal terrace, but with a scrobicular ring. Lower Carboniferous ; North 

 America. 



Family 2, Lepidocentridae Loven. 



Two columns of plates in each ambulacral area. Five to fourteen columns of 

 plates in an interambulacral area. Primordial interambulacral plates in basicoronal 

 row. Base of Corona not resorbed. Oculars insert. Genitals with many pores each. 

 Peristome with many rows of ambulacral plates only. Spines small eccentrically 



