CATALOGUE 
OF 
E C H I N I D A. 
Subdivision II. — Tbe Irregularia. 
Vent lateral, dorsal, or inferior (not in the middle of the back) ; 
body not globular, variously shaped ; jaws horizontal, sepa- 
rate or wanting ; anus and mouth covered with small scales ; 
ambulacra short, often confined to the vertex, and generally 
interrupted on the margin, sometimes appearing again near 
the mouth ; shell covered with numerous generally equal- 
sized bristle-like spines, rarely scattered with thicker and 
more elongated ones. 
Echinida, the annectant group, Gray, Ann. Phil. 1825, 5. 
Echinides, Sect. 2, part, and sect. 1 . Lamk. Hist. iii. 267. 
Irregularia, Latr. Fam. Nat. R. A. 533, 1825. 
Catocystos and Pleurocystos, Klein Echin. 13 ; Leske, 97-153. 
Section 1 . Mesostoma, mouth subcentral, round, or pentagular. 
Mesostoma, Latr. Fam. R. A. 533, 1825. 
Les Clypeastres, Agassiz , Prod. 
Les Echinides paracentrostome, Blainv. Diet. Sc. Nat. 
Clypeasteroidea, Agassiz ; Bronn, Gesch d. Nat. 193, 1846. 
Catocystos, part., Klein, 12. 
Emmesostomi, part., Klein, 37. 
Catocysti emmesostomi, part., Van Phelsum. 
Pieurocysti Emmesostomi, Van Phelsum. 
