70 SVEN LOVEN, ECHINOLOÖICA. 



ricles arise from the interradium. They are united into one 

 piece, broadly expanded at the base, faintly bilobated, fiy. 10'J. 

 The retractors are bipartite, attached to the auricde iiear its 

 margin, slightly desceiiding- adorally, and inserted rather low 

 on either side of the mesial ridge. The slender protractors are 

 attached between the lower parts of the retractors and inserted 

 a little above the middle of the under surface. The teetli, 

 Fl. IX, fuj. 102, Fl. XI, fl(j. 14], lå~>, long, low, slightly 

 curved outward, are more erect and capable of being protruded 

 than ill tlie other genera. Tlieir backs, of a triangulär sec- 

 tion, are received in the deep groove of the slide, their prismal 

 part being slightly more compressed than in the Laganum. 



Among the leading forms of the Odontuphora Irregularia 

 here reviewed with respect to their maxillary system, the 

 Echinocyamus has more of the Regularian type than any 

 other. The height of the whole system; the nearly erect po- 

 sition of the teeth, which are low and curved outward; the 

 form of the external surface of the pyramid, cordate, not ar- 

 row-headed, fii}. 104, 105, and the siniply hinate symphysis 

 recalling the Discoidea; tlie epiphysis, simplified in form but 

 still proportionally of conspicuous size; the nearly compact, not 

 lameliar nor lacunal structure of the wings, the two interiör of 

 which are slightly converging, all this, combined with the unin- 

 terrupted sequence of the uniform interradia, which are half as 

 broad as the likewise uniform ambulacra. but not compressed; 

 the pedicellar pores confined to the ambulacra, not spreading 

 upon the interradia;' the internal peritoneal layer forming 

 on every interradium two simple partitions like those of the 

 Galerites — , all this constitutes in the Echinocyamus an assem- 

 l)lage of approximations towards the Regularia, archaäonomous 

 features not inconsistent with the alleged but not fully con- 

 firmed early ai)pearance of the genus, earliest of the whole 

 tribe as far as at present known, in the cretaceous strata at 

 Maestricht.'- In these strata the genus Fibularia is also said 

 to be represen ted;^ it is very similar to Echinocyamus, but has 

 the lameliar structure of the wings fully developcd.^ 



Near to these two forms comes the genus Laganum, with 

 the teeth low, slightly curved outward, raised at an angle of 



' Études s. 1. Echinoidées, p. 32, 47, Pl. XLIV. 

 ^ E. placenta Gldp, Desor,. Synopsis p. 220. 

 ^ Fibularia subglobosa Gldf., ib. p. 221. 



