SEA-URCHIN'S. 443 



The classification adopted in 1840 by L. Agassiz, in lii.s 

 ' Catalogus systematicvis,' was in many ways of less value than 

 that of Klein ; for he grouped together, under the heading of 

 " Clypeastroidse," all the non-Spatangid Irregular Echinoids. 

 However, Desor, in the sequel to that Catalogue (11) showed that 

 a. more detailed system of subdivision was pi-acticable, and founded 

 the fii-st definite scheme of the classification of the group. The 

 "■ tribu " of the " Galerites " was regarded as a division of the 

 " Clypeastroides." It contained the following genera •.—Cara- 

 iomufi, JJIscoidea, Echinoneus, (hilerites, Glohator, Ilolectypus (as 

 a subgenus of Discoidea), Hi/hoch/jius, Nucleopygus, Pygaster^ and 

 Pyrina. This list of genera contains a very natural grouping of 

 all those Iiregular Echinoids which have simple, apetaloid 

 ambulacra. That, however, is almost the only trait that couki 

 associate them, and in Caratomus.j at least, the simplicity of the 

 ambulacra is not absolute. 



In the ' Catalogue raisonnee ' (1847) Agassiz and Desor retained 

 this grouping of the genera in its entirety, b\it i-earranged 

 the position of the "tribu" as a whole. It appears as the 

 family Echinoneidje, a section of the Cassidulidse. This change 

 was at once an advance and a retrogression. It applied to the 

 family a name under which some of the genera have remained 

 since that time, but by associating the whole series with the 

 Cassidulids, it tended to obsciu-e the importance of the gnatho- 

 stomatous character of many of tlie genera. 



In the Synopsis, Desor (21) retained the division under the 

 name of Galeiidees, and added lai'ge numbers of genera to the 

 list. He recognized, howevei-, the fundamental importance of 

 the presence of jaws in determining the systematic position of a 

 genus, and so separated the Galeridees into two groups. Of these, 

 the first, or " Galeridees proprement dits," contained fifteen 

 genera with jaws (or rather, supposed to possess them), while the 

 second, the " Echinonees," included Uchinoneus only. The first 

 groiip contained all the genera of the "Galei-ites " of 1842, excejit 

 Caratomv s and Echinoneus, and there were added the then newly 

 described geneia Anortliopygiis, Asierostoi)ia, Desorella, Galero- 

 pygus, Pachj/clypus, and Pileus. It is curious that Desor should 

 have taken it for granted that all these fossil genera were gnatho- 

 stomatous, for he cannot have had any positive evidence to work 

 upon in the majoiity of cases. 



In 1857 Pictet, in the second edition of his ' Paleontologie ' (22), 

 reverted to the method of grouping originated by Desor in 1842, 

 changing the word " Galerites"' to the subordinal term " Galeri- 

 tiens," and adding the then recently described Desoria. 



One year before the appeai-ance of Desor's Synopsis, Wright 

 (20) had grasped the essential differences which divided the 

 " Galerites " into two sections. He founded the family of the 

 Echinoconidpe, which contained Discoidea, Echiuocovus (the 

 Galerites of most previous authors), Jlolectypics, Hi/bodi/pus, and 



