Prof. Agassiz on the Echinodei'mata. 301 



subject at the period of the publication of this encyclopasdia. 

 Notwithstanding that it embraces these fossils in their totahty, 

 the great Avork of Goldfuss on the Petrifactions of Germany 

 Avill for a long time to come be a standard work for the study 

 of fossil Echinodermata. 



In the ' Nouveaux Memoires de la Soc. Helvetique des 

 Scien. JVaturclles ' (torn. ii. et iv.), I have made known the 

 fossil EcMnites of Switzerland ; my descriptions are accom- 

 panied with figures which represent all the species under va- 

 rious aspects. In this memoir I have established the follov.- 

 ing genera : — Hyboclyjms, Pygorhynchus^Conoclypus,Pygurus, 

 Hemicidaris, Acrocidaris, Acrosalenia, Tetragramma, Pedina, 

 and Glypticus. In the first volume of the ' Mem. de la Soc. 

 des Sc. Nat. de Neuchatel/ I had previously published, in 

 part, a notice on the species of the Neocomian formations; 

 since then, in my systematic catalogue of the casts of the 

 fossil Sea-urchins in the museum at Neuchatel *, I published 

 the essential characters of the new or little known genera 

 which I have established up to the present time amongst the 

 Echinites. The following genera are there characterized for 

 the first time : — Toxaster, Brissopsis, Nucleopygus, Globed or, 

 Caratomus,Amblypygns,Ibeliophora\,Amphiope,E7icope,Echi- 

 nopsis, Cyphosoma, Acropeltis, Cwlopleurus, Codiopsis, Podo- 

 jjJiora^ and Acrocladia. The distribution of many series of 

 these casts has given a publicity to my researches upon the 

 Echinites, which I hope will aid in advancing our knowledge 

 of these fossils, and facilitate the identification of specimens 

 which as yet may not be figured or even described. I have 

 also put into circulation representations, as faithful as it was 

 possible to obtain them, of a great number of unique speci- 

 mens in a ver}' perfect state of preservation. 



Since the publication, in 1838, of my first monograph upon 

 the Echinodermata, the materials at my disposal have been 

 greatly augmented. A number of new species in all the orders 

 of the class Echinodermata have been entrusted to me by the 

 numerous friends of science, who have considered that a most 

 efficacious way of serving it would be that of bringing toge- 

 ther, in the same publication, the greatest possible amount of 

 data. I therefore esteem it both a duty and pleasure to re- 

 cord here the names of all those who have acquired new 

 claims to my gratitude, whether it be in the communication 



* Catalogiis System. Ectyporuin Echiiiodermatum Fo:<siliuin Miisei Neo- 

 comensis, Ito, IS 10. 



f This genus lias since regained the name Rotala^ given to it more than 

 a century ago by Klein, but of whicli no one liud taken notice. 



