30 L. Agassiz on the Echinodermata. 



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

 streaks; covered with a thin pale brown laminar periostracum; 

 lunule and lozenge smooth, keeled; lateral teeth very thin. 

 — Hab. China. 



Very like M, Helvacea, but smaller and much more com- 

 pressed. 



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

 dermata, By Louis Agassiz, D.M.* 



Having 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 '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. 



