30 L. Agassiz on the Echinoih'r inula. 



thin, pellucid, pale, with whitish rays and darker submarginal 

 streaks; covered with a thin pale brown laminar periostracum; 

 liuinle and Lozenge smooth, keeled; lateral teeth very thin. 

 — Huh. China. 



Very like M. Helvacca, but smaller and much more com- 

 pressed. 



V. — Prodromus of a Monograph of the Radiata and Echino- 

 dermata. By Louis Agassiz, D.M.* 



Haying had occasion for some years to examine a great 

 number of Echinodermata, and having paid particular attention 

 to their general organization, but more especially to the solid 

 portions of their integument, which have been hitherto consi- 

 dered the most important of their external characteristics, I have 

 felt induced by these circumstances, and others no less favour- 

 able to inquiries of this kind, to publish the following outline 

 of a survey of the genera of this class as an introduction to a 

 more general and critical work, in which I purpose hereafter 

 to treat of all the species and their comparative anatomy. 



The section of radiated animals to which the Echinodermata 

 belong, should, in order to be characterised in a general man- 

 ner, be reduced to three classes : the Polypi, the Acalephae, and 

 the Echinodermata. Intestinal worms, and a great part, if not 

 the whole, of the Infusoria should be restored to the section 

 of articulated animals. That I may not be compelled for a 

 moment to lose sight of the main object of this paper, I think 

 it advisable, as M. de Blainville has already proposed some of 

 these changes, to refer for information as to the limitation of 

 these classes to the article "Zoophytes" in the f Dictionnaire des 

 Sciences Naturelles/ though there are several points of detail 

 on which he and I disagree. 



The class of the Echinodermata confined within its natural 

 limits should contain no more than the three genera Holothu- 

 ria, Echinus, and Asterias of Linnaeus, which have become the 



* Translated from the extract in the ' Annales des Sciences Naturelles,' 

 Mai 1837, taken from the ' Memoires de la Societe des Sciences Naturelles 

 de Neufchatel,' tome i. 



