CLASS I ECHINOIDEA 303 



Family 3. Palaeechinidae M'Coy. 



Test elliptical, obovate, sjyherical or subspheroidal. Two to twelve columns of 

 plates in each ambulacral area, three to eleven columns of plates in each inter- 

 .ambulacral area. Plates not imbricate, but ambulacral plates bevel over the 

 interambulacral on adradial sutures. Primordial interambulacral plates resorbed. 

 One row only of interambulacral plates resorbed in advance of the peristome. Oculars 

 usually all insert, genitals usually with three to five pores each. Peristome with 

 many rows of ambidacrcd and some interradial non-ambulacral plates (Fig. 371, D). 

 Secondary spines and imperforate tubercles only. Silurian (?), Lower Carboniferous. 



This family includes more species than any other in the Paleozoic. It 

 contains genera with complex ambulacra composed of more than two columns 

 of simple plates in an area, and the species in development pass through 

 stages like those of adults in all lower species or genera in the family. The 

 interambulacral plates are very definite in form, and the incoming of columns 

 indicate stages in development. 



Palaeechinus M'Coy (Figs. 367, i; 430; 431). Two columns of plates in 



d' 



Fig. 431. 



Palaeechinus elegans M'Coy. Lower Carboniferous Limestone ; Ireland. A, Test, i/i (after M'Coy). 

 B, Apical system, more than twice enlarged (after Jackson). 



each ambulacral area, consisting of plates which are all primaries ; pore-pairs 

 uniserial. Four to six columns of plates in each interambulacral area. In 

 this lowest genus the ambulacral detail is like that seen as a developing stage 

 in the higher genera of the family. The test is elliptical, P. quadriserialis, 

 or nearly spherical, P. elegans. Lower Carboniferous ; Europe and North 

 America. 



Maccoya Pomel (Fig. 367, k). Two columns of plates in each ambulacral 

 area, consisting of plates which are alternately primaries and partially or 

 completely occluded ; pore-pairs biserial. Four to eight or nine columns of 

 plates in each interambulacral area. In this genus, ventrally and dorsally, 

 ambulacral plates as stages in development are all primaries as in Palaeechinus. 

 M. phillipsiae Forbes is attributed to the Silurian (?) of England, other species 

 Lower Carboniferous ; Europe and North America. 



Lovenechinus Jackson (Figs. 367, I; 432). Four columns of plates in each 

 ambulacral area, consisting of demi- and occluded plates ; pore-pairs biserial. 

 Four to seven columns of plates in each interambulacral area. While in this 

 genus there are four columns of ambulacral plates at the mid-zone, primary 

 plates as a stage occur ventrally and dorsally, L. septies. In L. missiouriensis 

 (Jackson) primary with occluded plates exist both ventrally and dorsally as a 



