332 ECHINONEUS. 



bulacra, all based upon characters subject to great variation (lining growth, 

 show the necessity of a careful revision of the whole group of Spatangoids, 



especially of the fossil genera, with the data here furnished, before we can 

 attempt an arrangement of Spatangoids into natural families. 



CASSIDULIDAE. 



Family Casidulidae Agass. 1847. C. It. Ann. Sc. Nat. VII. 147. 



ECHINONIDAE. 



Subfamily Echinonidae Agass. 1847. C. R. Ann. Sc. Nat. VII. 147. 



The close structural resemblance between the young of Echinolampadae 

 and Echinoneus shows that Echinoneus has no affinity whatever with the 

 Galeritidae, with which the genus has always been associated, but that it is a 

 true embryonic Cassidulus allied to Echinolampadae and Caratomus, already 

 suggested by Desor to be a true Cassidulus, and not a Galerites. This allinitv 

 the examination of young Echinolampadae proves undoubtedly. The removal 

 of Echinoneus. Caratomus, and all the allied edentate forms of Galerites, now 

 reduces the family to one of great homogeneity, and suggests again the ques- 

 tion of their allinitv to true, regular Echinoids in a more forcible manner 

 than before. We must, however, wait till we find a living representative of 

 Galerites to have the question fully decided. I am inclined, in the mean 

 while, to associate the Galeritidae having teeth with the true Echinoids, and 

 consider them as forming among Echinoids a prophetic type of the Clypeas- 

 troids, with which they have many points of resemblance. 



This subfamily contains elliptical subovoid Echini, with simple ambulacra 

 and remarkably uniform sunken tubercles ; no jaws. 



ECHINONEUS. 



Echinoneus Van Phel. 1774. Brief. 



This genus has been very generally placed as a subfamily among the 

 Galeritidae. The embryology of Echinolampas shows conclusively that this 

 association is not natural, and that the view first maintained by Liitken of 

 its Cassiduloid affinity is the correct one. Thus far, Echinoneus is the only 



