ECHINI 



Eastern Coast of the United States. 



DESMOSTICHA. 



Suborder Desmosticha Haeckel, Entwiekel. Gesch. 186G. (emend.) 



CIDARIDAE. 



Family Cidaridae Mull. Bau der Echin. 1854 (emend.) 



GONIOCIDARXDAE. 



Subfamily Goniocidarida Haeckel, Entwiekel. Gesch. 



TnE subordinal divisions usually adopted since their introduction by Albin 

 Gras do not seem satisfactory, if tested by our present information. In the 

 first place, the whole classification is based upon the separation of the anus 

 from the abactinal system. From what the embryology of Echini has taught 

 us, the position of the anus has not the physiological importance attributed 

 to it by authors who have so generally received this classification. The 

 unstable position it occupies in the same animal at different stages of growth 

 — at one stage opening next to the mouth, then on the margin, and finally 

 opening in the central part of the apical system in the adult — should make 

 us hesitate to adopt a single anatomical feature as our sole guide. In the 

 first place, the order of Perischoechinidae, a most natural one, is founded upon 

 characters derived from the structure of the interambulacral and ambulacral 

 systems. The other two suborders, regular and irregular, usually recognized, 

 can scarcely be called natural. The suborder of regular Echini is more sat- 

 isfactory than the other, though, from what I have said in the Preliminary 

 Report of the Galerites with teeth, I should be inclined to add them to the 

 suborder of the regular Echini (Desmosticha), as one of its three primary 

 subdivisions, which, as here limited, are the Cidaridae, the Echinidae proper, 

 and the Galerites. The suborder of " irregular " Echini, after the with- 



